diff --git a/src/Auth/DigestAuthenticate.php b/src/Auth/DigestAuthenticate.php
index 01d1d60af10..1329fb0368d 100644
--- a/src/Auth/DigestAuthenticate.php
+++ b/src/Auth/DigestAuthenticate.php
@@ -132,7 +132,7 @@ public function getUser(ServerRequest $request)
      * Gets the digest headers from the request/environment.
      *
      * @param \Cake\Http\ServerRequest $request Request object.
-     * @return array Array of digest information.
+     * @return array|bool Array of digest information.
      */
     protected function _getDigest(ServerRequest $request)
     {
diff --git a/src/Auth/Storage/MemoryStorage.php b/src/Auth/Storage/MemoryStorage.php
index 12d9c0f7474..ab9cbc68a09 100644
--- a/src/Auth/Storage/MemoryStorage.php
+++ b/src/Auth/Storage/MemoryStorage.php
@@ -30,7 +30,7 @@ class MemoryStorage implements StorageInterface
     /**
      * Redirect url.
      *
-     * @var string
+     * @var string|null
      */
     protected $_redirectUrl;
 
diff --git a/src/Cache/Cache.php b/src/Cache/Cache.php
index 4a35c096a74..ea5d65f7510 100644
--- a/src/Cache/Cache.php
+++ b/src/Cache/Cache.php
@@ -102,7 +102,7 @@ class Cache
     /**
      * Cache Registry used for creating and using cache adapters.
      *
-     * @var \Cake\Cache\CacheRegistry
+     * @var \Cake\Core\ObjectRegistry
      */
     protected static $_registry;
 
diff --git a/src/Cache/Engine/FileEngine.php b/src/Cache/Engine/FileEngine.php
index 3f4ea7e6222..4c49f41c61c 100644
--- a/src/Cache/Engine/FileEngine.php
+++ b/src/Cache/Engine/FileEngine.php
@@ -36,7 +36,7 @@ class FileEngine extends CacheEngine
     /**
      * Instance of SplFileObject class
      *
-     * @var \SplFileObject
+     * @var \SplFileObject|null
      */
     protected $_File = null;
 
diff --git a/src/Cache/Engine/WincacheEngine.php b/src/Cache/Engine/WincacheEngine.php
index 8260429445d..ddf63fb524a 100644
--- a/src/Cache/Engine/WincacheEngine.php
+++ b/src/Cache/Engine/WincacheEngine.php
@@ -204,7 +204,7 @@ public function groups()
      */
     public function clearGroup($group)
     {
-        $success = null;
+        $success = false;
         wincache_ucache_inc($this->_config['prefix'] . $group, 1, $success);
 
         return $success;
diff --git a/src/Collection/Iterator/MapReduce.php b/src/Collection/Iterator/MapReduce.php
index 077fffdf2c4..bf57cc8bc9e 100644
--- a/src/Collection/Iterator/MapReduce.php
+++ b/src/Collection/Iterator/MapReduce.php
@@ -52,7 +52,7 @@ class MapReduce implements IteratorAggregate
     /**
      * Holds the original data that needs to be processed
      *
-     * @var \Traversable
+     * @var \Traversable|null
      */
     protected $_data;
 
@@ -74,7 +74,7 @@ class MapReduce implements IteratorAggregate
     /**
      * Count of elements emitted during the Reduce phase
      *
-     * @var string
+     * @var int
      */
     protected $_counter = 0;
 
diff --git a/src/Console/ConsoleInputSubcommand.php b/src/Console/ConsoleInputSubcommand.php
index 26042bd073e..68e9ad0ebc1 100644
--- a/src/Console/ConsoleInputSubcommand.php
+++ b/src/Console/ConsoleInputSubcommand.php
@@ -102,7 +102,7 @@ public function help($width = 0)
     /**
      * Get the usage value for this option
      *
-     * @return mixed Either false or a ConsoleOptionParser
+     * @return \Cake\Console\ConsoleOptionParser|bool Either false or a ConsoleOptionParser
      */
     public function parser()
     {
diff --git a/src/Console/ConsoleOptionParser.php b/src/Console/ConsoleOptionParser.php
index 7aedc4de392..e53482759b0 100644
--- a/src/Console/ConsoleOptionParser.php
+++ b/src/Console/ConsoleOptionParser.php
@@ -100,7 +100,7 @@ class ConsoleOptionParser
     /**
      * Map of short -> long options, generated when using addOption()
      *
-     * @var string
+     * @var array
      */
     protected $_shortOptions = [];
 
@@ -501,7 +501,7 @@ public function addArgument($name, array $params = [])
             if ($a->isEqualTo($arg)) {
                 return $this;
             }
-            if ($options['required'] && !$a->isRequired()) {
+            if (!empty($options['required']) && !$a->isRequired()) {
                 throw new LogicException('A required argument cannot follow an optional one');
             }
         }
diff --git a/src/Console/ConsoleOutput.php b/src/Console/ConsoleOutput.php
index 93e02652295..e31a7f19875 100644
--- a/src/Console/ConsoleOutput.php
+++ b/src/Console/ConsoleOutput.php
@@ -119,9 +119,9 @@ class ConsoleOutput
     ];
 
     /**
-     * formatting options for colored output
+     * Formatting options for colored output.
      *
-     * @var string
+     * @var array
      */
     protected static $_options = [
         'bold' => 1,
diff --git a/src/Console/HelpFormatter.php b/src/Console/HelpFormatter.php
index 74eabdf2dd8..fcf7cf0824c 100644
--- a/src/Console/HelpFormatter.php
+++ b/src/Console/HelpFormatter.php
@@ -210,6 +210,6 @@ public function xml($string = true)
             $argument->xml($arguments);
         }
 
-        return $string ? $xml->asXml() : $xml;
+        return $string ? $xml->asXML() : $xml;
     }
 }
diff --git a/src/Console/Shell.php b/src/Console/Shell.php
index 859f0782c07..18554477401 100644
--- a/src/Console/Shell.php
+++ b/src/Console/Shell.php
@@ -129,7 +129,7 @@ class Shell
     /**
      * Contains tasks to load and instantiate
      *
-     * @var array
+     * @var array|bool
      * @link http://book.cakephp.org/3.0/en/console-and-shells.html#Shell::$tasks
      */
     public $tasks = [];
diff --git a/src/Controller/Component/AuthComponent.php b/src/Controller/Component/AuthComponent.php
index b370a34bfce..5c1d2b42349 100644
--- a/src/Controller/Component/AuthComponent.php
+++ b/src/Controller/Component/AuthComponent.php
@@ -192,7 +192,7 @@ class AuthComponent extends Component
     /**
      * Storage object.
      *
-     * @var \Cake\Auth\Storage\StorageInterface
+     * @var \Cake\Auth\Storage\StorageInterface|null
      */
     protected $_storage;
 
diff --git a/src/Controller/Component/CookieComponent.php b/src/Controller/Component/CookieComponent.php
index 9113c419d9c..7c1e97426cd 100644
--- a/src/Controller/Component/CookieComponent.php
+++ b/src/Controller/Component/CookieComponent.php
@@ -85,7 +85,7 @@ class CookieComponent extends Component
      *
      * Accessed in the controller using $this->Cookie->read('Name.key');
      *
-     * @var string
+     * @var array
      */
     protected $_values = [];
 
@@ -104,7 +104,7 @@ class CookieComponent extends Component
      * A reference to the Controller's Cake\Network\Response object.
      * Currently unused.
      *
-     * @var \Cake\Network\Response
+     * @var \Cake\Network\Response|null
      * @deprecated 3.4.0 Will be removed in 4.0.0
      */
     protected $_response = null;
diff --git a/src/Controller/Component/SecurityComponent.php b/src/Controller/Component/SecurityComponent.php
index 7677b541305..8fdcd8f14a5 100644
--- a/src/Controller/Component/SecurityComponent.php
+++ b/src/Controller/Component/SecurityComponent.php
@@ -637,7 +637,7 @@ protected function _matchExistingFields($dataFields, &$expectedFields, $intKeyMe
      *
      * @param array $expectedFields Expected fields
      * @param string $missingMessage Message template
-     * @return string Error message about expected fields
+     * @return string|null Error message about expected fields
      */
     protected function _debugExpectedFields($expectedFields = [], $missingMessage = '')
     {
diff --git a/src/Database/Connection.php b/src/Database/Connection.php
index f2ba0dd2c31..5b77e41f140 100644
--- a/src/Database/Connection.php
+++ b/src/Database/Connection.php
@@ -88,9 +88,9 @@ class Connection implements ConnectionInterface
     /**
      * The schema collection object
      *
-     * @var \Cake\Database\Schema\Collection
+     * @var \Cake\Database\Schema\Collection|null
      */
-    protected $_schemaCollection;
+    protected $_schemaCollection = null;
 
     /**
      * Constructor.
@@ -612,7 +612,7 @@ public function rollbackSavepoint($name)
      */
     public function disableForeignKeys()
     {
-        $this->execute($this->_driver->disableForeignKeySql())->closeCursor();
+        $this->execute($this->_driver->disableForeignKeySQL())->closeCursor();
     }
 
     /**
@@ -622,7 +622,7 @@ public function disableForeignKeys()
      */
     public function enableForeignKeys()
     {
-        $this->execute($this->_driver->enableForeignKeySql())->closeCursor();
+        $this->execute($this->_driver->enableForeignKeySQL())->closeCursor();
     }
 
     /**
diff --git a/src/Database/Dialect/SqlserverDialectTrait.php b/src/Database/Dialect/SqlserverDialectTrait.php
index 3617ffa2c68..b883ad84f09 100644
--- a/src/Database/Dialect/SqlserverDialectTrait.php
+++ b/src/Database/Dialect/SqlserverDialectTrait.php
@@ -298,7 +298,7 @@ protected function _transformFunctionExpression(FunctionExpression $expression)
      * Used by Cake\Schema package to reflect schema and
      * generate schema.
      *
-     * @return \Cake\Database\Schema\MysqlSchema
+     * @return \Cake\Database\Schema\SqlserverSchema
      */
     public function schemaDialect()
     {
diff --git a/src/Database/Driver.php b/src/Database/Driver.php
index 97d4aef533d..3839319f386 100644
--- a/src/Database/Driver.php
+++ b/src/Database/Driver.php
@@ -86,7 +86,7 @@ abstract public function disconnect();
      * If first argument is passed,
      *
      * @param null|\PDO $connection The connection object
-     * @return void
+     * @return \Cake\Database\Connection
      */
     abstract public function connection($connection = null);
 
@@ -258,7 +258,7 @@ public function schemaValue($value)
             is_numeric($value) && strpos($value, ',') === false &&
             $value[0] !== '0' && strpos($value, 'e') === false)
         ) {
-            return $value;
+            return (string)$value;
         }
 
         return $this->_connection->quote($value, PDO::PARAM_STR);
diff --git a/src/Database/Driver/PDODriverTrait.php b/src/Database/Driver/PDODriverTrait.php
index 593b36e1828..a4a6ff86146 100644
--- a/src/Database/Driver/PDODriverTrait.php
+++ b/src/Database/Driver/PDODriverTrait.php
@@ -27,9 +27,9 @@ trait PDODriverTrait
     /**
      * Instance of PDO.
      *
-     * @var \PDO
+     * @var \PDO|null
      */
-    protected $_connection;
+    protected $_connection = null;
 
     /**
      * Establishes a connection to the database server
@@ -79,7 +79,7 @@ public function disconnect()
     }
 
     /**
-     * Check whether or not the driver is connected.
+     * Checks whether or not the driver is connected.
      *
      * @return bool
      */
@@ -94,9 +94,8 @@ public function isConnected()
                 $connected = false;
             }
         }
-        $this->connected = !empty($connected);
 
-        return $this->connected;
+        return (bool)$connected;
     }
 
     /**
diff --git a/src/Database/Expression/Comparison.php b/src/Database/Expression/Comparison.php
index 2edd09d30ed..bfa75e3864d 100644
--- a/src/Database/Expression/Comparison.php
+++ b/src/Database/Expression/Comparison.php
@@ -42,7 +42,7 @@ class Comparison implements ExpressionInterface, FieldInterface
     /**
      * The type to be used for casting the value to a database representation
      *
-     * @var string
+     * @var string|array
      */
     protected $_type;
 
diff --git a/src/Database/Expression/ValuesExpression.php b/src/Database/Expression/ValuesExpression.php
index a19bda618f7..1cdd3c70ec0 100644
--- a/src/Database/Expression/ValuesExpression.php
+++ b/src/Database/Expression/ValuesExpression.php
@@ -60,7 +60,7 @@ class ValuesExpression implements ExpressionInterface
      * Whether or not values have been casted to expressions
      * already.
      *
-     * @var string
+     * @var bool
      */
     protected $_castedExpressions = false;
 
diff --git a/src/Database/Log/LoggedQuery.php b/src/Database/Log/LoggedQuery.php
index cb528fcb56c..0cc71312364 100644
--- a/src/Database/Log/LoggedQuery.php
+++ b/src/Database/Log/LoggedQuery.php
@@ -33,14 +33,14 @@ class LoggedQuery
     /**
      * Number of milliseconds this query took to complete
      *
-     * @var float
+     * @var int
      */
     public $took = 0;
 
     /**
      * Associative array with the params bound to the query string
      *
-     * @var string
+     * @var array
      */
     public $params = [];
 
@@ -54,7 +54,7 @@ class LoggedQuery
     /**
      * The exception that was thrown by the execution of this query
      *
-     * @var \Exception
+     * @var \Exception|null
      */
     public $error;
 
diff --git a/src/Database/Log/LoggingStatement.php b/src/Database/Log/LoggingStatement.php
index 9ebf08f595a..ec8b6e9038b 100644
--- a/src/Database/Log/LoggingStatement.php
+++ b/src/Database/Log/LoggingStatement.php
@@ -28,7 +28,7 @@ class LoggingStatement extends StatementDecorator
     /**
      * Logger instance responsible for actually doing the logging task
      *
-     * @var \Cake\Database\Log\QueryLogger
+     * @var \Cake\Database\Log\QueryLogger|null
      */
     protected $_logger;
 
@@ -110,7 +110,7 @@ public function bindValue($column, $value, $type = 'string')
      * it returns the currently setup logger instance
      *
      * @param object|null $instance Logger object instance.
-     * @return object Logger instance
+     * @return object|null Logger instance
      */
     public function logger($instance = null)
     {
diff --git a/src/Database/Query.php b/src/Database/Query.php
index f959bf3b028..48f92626e1b 100644
--- a/src/Database/Query.php
+++ b/src/Database/Query.php
@@ -1618,7 +1618,7 @@ public function func()
      * iterated without having to call execute() manually, thus making it look like
      * a result set instead of the query itself.
      *
-     * @return \Iterator
+     * @return \Cake\Database\StatementInterface|null
      */
     public function getIterator()
     {
diff --git a/src/Database/Schema/TableSchema.php b/src/Database/Schema/TableSchema.php
index 3c98a2579c4..58fcc6e85f3 100644
--- a/src/Database/Schema/TableSchema.php
+++ b/src/Database/Schema/TableSchema.php
@@ -399,7 +399,7 @@ public function columnType($name, $type = null)
      * based upon.
      *
      * @param string $column The column name to get the base type from
-     * @return string The base type name
+     * @return string|null The base type name
      */
     public function baseColumnType($column)
     {
diff --git a/src/Database/Statement/BufferedStatement.php b/src/Database/Statement/BufferedStatement.php
index 3168d793722..70683c73859 100644
--- a/src/Database/Statement/BufferedStatement.php
+++ b/src/Database/Statement/BufferedStatement.php
@@ -46,6 +46,7 @@ class BufferedStatement extends StatementDecorator
 
     /**
      * Current record pointer
+     *
      * @var int
      */
     protected $_counter = 0;
diff --git a/src/Database/Statement/StatementDecorator.php b/src/Database/Statement/StatementDecorator.php
index 2d57e506071..42fe0529bed 100644
--- a/src/Database/Statement/StatementDecorator.php
+++ b/src/Database/Statement/StatementDecorator.php
@@ -37,7 +37,7 @@ class StatementDecorator implements StatementInterface, Countable, IteratorAggre
      * Statement instance implementation, such as PDOStatement
      * or any other custom implementation.
      *
-     * @var mixed
+     * @var \Cake\Database\StatementInterface
      */
     protected $_statement;
 
diff --git a/src/Database/Type.php b/src/Database/Type.php
index b9c456eea2e..be402b131a0 100644
--- a/src/Database/Type.php
+++ b/src/Database/Type.php
@@ -269,7 +269,7 @@ public static function boolval($value)
      * Will convert values into strings
      *
      * @param mixed $value The value to convert to a string.
-     * @return bool
+     * @return string
      * @deprecated 3.1.8 This method is now unused.
      */
     public static function strval($value)
diff --git a/src/Database/Type/DecimalType.php b/src/Database/Type/DecimalType.php
index 962e32206ae..675a4e16fa8 100644
--- a/src/Database/Type/DecimalType.php
+++ b/src/Database/Type/DecimalType.php
@@ -72,7 +72,7 @@ public function toDatabase($value, Driver $driver)
      *
      * @param null|string|resource $value The value to convert.
      * @param \Cake\Database\Driver $driver The driver instance to convert with.
-     * @return float
+     * @return float|null
      * @throws \Cake\Core\Exception\Exception
      */
     public function toPHP($value, Driver $driver)
diff --git a/src/Database/Type/FloatType.php b/src/Database/Type/FloatType.php
index f365d7ddfdf..1d36ea63e02 100644
--- a/src/Database/Type/FloatType.php
+++ b/src/Database/Type/FloatType.php
@@ -48,7 +48,7 @@ class FloatType extends Type implements TypeInterface
      *
      * @param string|resource $value The value to convert.
      * @param \Cake\Database\Driver $driver The driver instance to convert with.
-     * @return string|null
+     * @return float|null
      */
     public function toDatabase($value, Driver $driver)
     {
@@ -64,7 +64,7 @@ public function toDatabase($value, Driver $driver)
      *
      * @param null|string|resource $value The value to convert.
      * @param \Cake\Database\Driver $driver The driver instance to convert with.
-     * @return resource
+     * @return float|null
      * @throws \Cake\Core\Exception\Exception
      */
     public function toPHP($value, Driver $driver)
@@ -73,7 +73,7 @@ public function toPHP($value, Driver $driver)
             return null;
         }
         if (is_array($value)) {
-            return 1;
+            return 1.0;
         }
 
         return (float)$value;
@@ -95,7 +95,7 @@ public function toStatement($value, Driver $driver)
      * Marshalls request data into PHP floats.
      *
      * @param mixed $value The value to convert.
-     * @return mixed Converted value.
+     * @return float|null Converted value.
      */
     public function marshal($value)
     {
@@ -109,7 +109,7 @@ public function marshal($value)
             return $this->_parseValue($value);
         }
         if (is_array($value)) {
-            return 1;
+            return 1.0;
         }
 
         return $value;
diff --git a/src/Database/Type/IntegerType.php b/src/Database/Type/IntegerType.php
index 1beb94fb28e..38a5adbc855 100644
--- a/src/Database/Type/IntegerType.php
+++ b/src/Database/Type/IntegerType.php
@@ -33,7 +33,7 @@ class IntegerType extends Type implements TypeInterface
      *
      * @param mixed $value The value to convert.
      * @param \Cake\Database\Driver $driver The driver instance to convert with.
-     * @return int
+     * @return int|null
      */
     public function toDatabase($value, Driver $driver)
     {
@@ -53,7 +53,7 @@ public function toDatabase($value, Driver $driver)
      *
      * @param mixed $value The value to convert.
      * @param \Cake\Database\Driver $driver The driver instance to convert with.
-     * @return int
+     * @return int|null
      */
     public function toPHP($value, Driver $driver)
     {
diff --git a/src/Datasource/QueryTrait.php b/src/Datasource/QueryTrait.php
index 05eaec47719..4ec18deb0bb 100644
--- a/src/Datasource/QueryTrait.php
+++ b/src/Datasource/QueryTrait.php
@@ -37,7 +37,7 @@ trait QueryTrait
      *
      * When set, query execution will be bypassed.
      *
-     * @var \Cake\Datasource\ResultSetInterface
+     * @var \Cake\Datasource\ResultSetInterface|null
      * @see \Cake\Datasource\QueryTrait::setResult()
      */
     protected $_results;
@@ -265,7 +265,7 @@ public function aliasFields($fields, $defaultAlias = null)
      */
     public function all()
     {
-        if (isset($this->_results)) {
+        if ($this->_results !== null) {
             return $this->_results;
         }
 
diff --git a/src/Error/Debugger.php b/src/Error/Debugger.php
index c80003abc7b..bfd403a9ecb 100644
--- a/src/Error/Debugger.php
+++ b/src/Error/Debugger.php
@@ -62,7 +62,7 @@ class Debugger
      * Templates used when generating trace or error strings. Can be global or indexed by the format
      * value used in $_outputFormat.
      *
-     * @var string
+     * @var array
      */
     protected $_templates = [
         'log' => [
@@ -98,7 +98,7 @@ class Debugger
     /**
      * Holds current output data when outputFormat is false.
      *
-     * @var string
+     * @var array
      */
     protected $_data = [];
 
@@ -163,13 +163,13 @@ public function __construct()
      * Returns a reference to the Debugger singleton object instance.
      *
      * @param string|null $class Class name.
-     * @return object|Debugger
+     * @return object|\Cake\Error\Debugger
      */
     public static function getInstance($class = null)
     {
         static $instance = [];
         if (!empty($class)) {
-            if (!$instance || strtolower($class) != strtolower(get_class($instance[0]))) {
+            if (!$instance || strtolower($class) !== strtolower(get_class($instance[0]))) {
                 $instance[0] = new $class();
             }
         }
diff --git a/src/Error/ExceptionRenderer.php b/src/Error/ExceptionRenderer.php
index 1008848ed6b..bb829fc574c 100644
--- a/src/Error/ExceptionRenderer.php
+++ b/src/Error/ExceptionRenderer.php
@@ -50,12 +50,19 @@
 class ExceptionRenderer implements ExceptionRendererInterface
 {
 
+    /**
+     * The exception being handled.
+     *
+     * @var \Exception
+     */
+    public $error;
+
     /**
      * Controller instance.
      *
      * @var \Cake\Controller\Controller
      */
-    public $controller = null;
+    public $controller;
 
     /**
      * Template to render for Cake\Core\Exception\Exception
@@ -71,13 +78,6 @@ class ExceptionRenderer implements ExceptionRendererInterface
      */
     public $method = '';
 
-    /**
-     * The exception being handled.
-     *
-     * @var \Exception
-     */
-    public $error = null;
-
     /**
      * Creates the controller to perform rendering on the error response.
      * If the error is a Cake\Core\Exception\Exception it will be converted to either a 400 or a 500
diff --git a/src/Event/Event.php b/src/Event/Event.php
index bdd11c85014..00a636fe9c9 100644
--- a/src/Event/Event.php
+++ b/src/Event/Event.php
@@ -188,7 +188,7 @@ public function setResult($value = null)
      * Access the event data/payload.
      *
      * @param string|null $key The data payload element to return, or null to return all data.
-     * @return array|null The data payload if $key is null, or the data value for the given $key. If the $key does not
+     * @return mixed[]|mixed|null The data payload if $key is null, or the data value for the given $key. If the $key does not
      * exist a null value is returned.
      */
     public function data($key = null)
diff --git a/src/Filesystem/Folder.php b/src/Filesystem/Folder.php
index 173bcde9d6f..cc2d9bbbc5d 100644
--- a/src/Filesystem/Folder.php
+++ b/src/Filesystem/Folder.php
@@ -167,7 +167,7 @@ public function pwd()
      * Change directory to $path.
      *
      * @param string $path Path to the directory to change to
-     * @return string The new path. Returns false on failure
+     * @return string|bool The new path. Returns false on failure
      */
     public function cd($path)
     {
@@ -924,7 +924,7 @@ public function errors($reset = true)
      * Get the real path (taking ".." and such into account)
      *
      * @param string $path Path to resolve
-     * @return string The resolved path
+     * @return string|bool The resolved path
      */
     public function realpath($path)
     {
diff --git a/src/Http/ActionDispatcher.php b/src/Http/ActionDispatcher.php
index f8691166480..96cd8ca3245 100644
--- a/src/Http/ActionDispatcher.php
+++ b/src/Http/ActionDispatcher.php
@@ -67,8 +67,8 @@ public function __construct($factory = null, $eventManager = null, array $filter
      * Dispatches a Request & Response
      *
      * @param \Cake\Http\ServerRequest $request The request to dispatch.
-     * @param \Cake\Network\Response $response The response to dispatch.
-     * @return \Cake\Network\Response A modified/replaced response.
+     * @param \Cake\Http\Response $response The response to dispatch.
+     * @return \Cake\Http\Response A modified/replaced response.
      */
     public function dispatch(ServerRequest $request, Response $response)
     {
diff --git a/src/Http/Client/Adapter/Stream.php b/src/Http/Client/Adapter/Stream.php
index 41fa7bdb20c..74b111e45a4 100644
--- a/src/Http/Client/Adapter/Stream.php
+++ b/src/Http/Client/Adapter/Stream.php
@@ -29,7 +29,7 @@ class Stream
     /**
      * Context resource used by the stream API.
      *
-     * @var resource
+     * @var resource|null
      */
     protected $_context;
 
@@ -50,7 +50,7 @@ class Stream
     /**
      * The stream resource.
      *
-     * @var resource
+     * @var resource|null
      */
     protected $_stream;
 
@@ -71,7 +71,7 @@ class Stream
     public function send(Request $request, array $options)
     {
         $this->_stream = null;
-        $this->_context = [];
+        $this->_context = null;
         $this->_contextOptions = [];
         $this->_sslContextOptions = [];
         $this->_connectionErrors = [];
diff --git a/src/Http/ControllerFactory.php b/src/Http/ControllerFactory.php
index aad6136a8e8..ce56d28cd20 100644
--- a/src/Http/ControllerFactory.php
+++ b/src/Http/ControllerFactory.php
@@ -62,16 +62,16 @@ public function create(ServerRequest $request, Response $response)
             strpos($controller, '.') !== false ||
             $firstChar === strtolower($firstChar)
         ) {
-            return $this->missingController($request);
+            $this->missingController($request);
         }
 
         $className = App::className($pluginPath . $controller, $namespace, 'Controller');
         if (!$className) {
-            return $this->missingController($request);
+            $this->missingController($request);
         }
         $reflection = new ReflectionClass($className);
         if ($reflection->isAbstract() || $reflection->isInterface()) {
-            return $this->missingController($request);
+            $this->missingController($request);
         }
 
         return $reflection->newInstance($request, $response, $controller);
diff --git a/src/Http/Response.php b/src/Http/Response.php
index d4eb673e79b..26f20c41b72 100644
--- a/src/Http/Response.php
+++ b/src/Http/Response.php
@@ -479,7 +479,7 @@ protected function _createStream()
      * Sends the complete response to the client including headers and message body.
      * Will echo out the content in the response body.
      *
-     * @return void
+     * @return void|null
      * @deprecated 3.4.0 Will be removed in 4.0.0
      */
     public function send()
diff --git a/src/Http/ResponseTransformer.php b/src/Http/ResponseTransformer.php
index a2aae538b4d..d3b29f98e72 100644
--- a/src/Http/ResponseTransformer.php
+++ b/src/Http/ResponseTransformer.php
@@ -133,7 +133,7 @@ protected static function parseCookies(array $cookieHeader)
      * Convert a PSR7 Response headers into a flat array
      *
      * @param \Psr\Http\Message\ResponseInterface $response The response to convert.
-     * @return \Cake\Network\Response The equivalent CakePHP response
+     * @return array Headers.
      */
     protected static function collapseHeaders(PsrResponse $response)
     {
diff --git a/src/Http/ServerRequestFactory.php b/src/Http/ServerRequestFactory.php
index be4f91aeaa4..7954e2b05c0 100644
--- a/src/Http/ServerRequestFactory.php
+++ b/src/Http/ServerRequestFactory.php
@@ -115,7 +115,7 @@ public static function marshalUriFromServer(array $server, array $headers)
      *
      * @param string $base The base path to remove.
      * @param \Psr\Http\Message\UriInterface $uri The uri to update.
-     * @return \Psr\Http\Message\ServerRequestInterface The modified Uri instance.
+     * @return \Psr\Http\Message\UriInterface The modified Uri instance.
      */
     protected static function updatePath($base, $uri)
     {
diff --git a/src/I18n/I18n.php b/src/I18n/I18n.php
index e9ef7f4c487..7f120a69839 100644
--- a/src/I18n/I18n.php
+++ b/src/I18n/I18n.php
@@ -38,9 +38,9 @@ class I18n
     /**
      * The translators collection
      *
-     * @var \Aura\Intl\TranslatorLocator
+     * @var \Aura\Intl\TranslatorLocator|null
      */
-    protected static $_collection;
+    protected static $_collection = null;
 
     /**
      * The environment default locale
@@ -54,7 +54,7 @@ class I18n
      * for getting specific translators based of their name and locale
      * or to configure some aspect of future translations that are not yet constructed.
      *
-     * @return \Aura\Intl\TranslatorLocator The translators collection.
+     * @return \Aura\Intl\TranslatorLocator|\Cake\I18n\TranslatorRegistry The translators collection.
      */
     public static function translators()
     {
@@ -121,7 +121,7 @@ public static function translators()
      * @param string|null $locale The locale for the translator.
      * @param callable|null $loader A callback function or callable class responsible for
      * constructing a translations package instance.
-     * @return \Aura\Intl\Translator|null The configured translator.
+     * @return \Aura\Intl\TranslatorInterface|null The configured translator.
      */
     public static function translator($name = 'default', $locale = null, callable $loader = null)
     {
diff --git a/src/I18n/Number.php b/src/I18n/Number.php
index d20853dcab3..f14d0ffa63c 100644
--- a/src/I18n/Number.php
+++ b/src/I18n/Number.php
@@ -50,9 +50,9 @@ class Number
     /**
      * Default currency used by Number::currency()
      *
-     * @var string
+     * @var string|null
      */
-    protected static $_defaultCurrency;
+    protected static $_defaultCurrency = null;
 
     /**
      * Formats a number with a level of precision.
diff --git a/src/I18n/Time.php b/src/I18n/Time.php
index b3df5b99dbc..f3679590e4c 100644
--- a/src/I18n/Time.php
+++ b/src/I18n/Time.php
@@ -65,7 +65,7 @@ class Time extends MutableDateTime implements JsonSerializable
      * The format to use when formatting a time using `Cake\I18n\Time::timeAgoInWords()`
      * and the difference is more than `Cake\I18n\Time::$wordEnd`
      *
-     * @var string
+     * @var string|array|int
      * @see \Cake\I18n\Time::timeAgoInWords()
      */
     public static $wordFormat = [IntlDateFormatter::SHORT, -1];
@@ -108,7 +108,7 @@ class Time extends MutableDateTime implements JsonSerializable
     public function __construct($time = null, $tz = null)
     {
         if ($time instanceof DateTimeInterface) {
-            $tz = $time->getTimeZone();
+            $tz = $time->getTimezone();
             $time = $time->format('Y-m-d H:i:s');
         }
 
diff --git a/src/I18n/TranslatorRegistry.php b/src/I18n/TranslatorRegistry.php
index 5d26ddd9558..105b0b5b3e8 100644
--- a/src/I18n/TranslatorRegistry.php
+++ b/src/I18n/TranslatorRegistry.php
@@ -128,7 +128,7 @@ public function setCacher(CacheEngine $cacher)
      * @param string $name The translator package to retrieve.
      * @param string|null $locale The locale to use; if empty, uses the default
      * locale.
-     * @return \Aura\Intl\TranslatorInterface A translator object.
+     * @return \Aura\Intl\TranslatorInterface|null A translator object.
      * @throws \Aura\Intl\Exception If no translator with that name could be found
      * for the given locale.
      */
diff --git a/src/Log/Log.php b/src/Log/Log.php
index 9355d14dfb9..1929cae8eec 100644
--- a/src/Log/Log.php
+++ b/src/Log/Log.php
@@ -129,9 +129,9 @@ class Log
     /**
      * LogEngineRegistry class
      *
-     * @var \Cake\Log\LogEngineRegistry
+     * @var \Cake\Log\LogEngineRegistry|null
      */
-    protected static $_registry;
+    protected static $_registry = null;
 
     /**
      * Handled log levels
diff --git a/src/Mailer/Email.php b/src/Mailer/Email.php
index ace217a6350..63762a6ea80 100644
--- a/src/Mailer/Email.php
+++ b/src/Mailer/Email.php
@@ -222,7 +222,7 @@ class Email implements JsonSerializable, Serializable
     /**
      * The transport instance to use for sending mail.
      *
-     * @var \Cake\Mailer\AbstractTransport
+     * @var \Cake\Mailer\AbstractTransport|null
      */
     protected $_transport = null;
 
@@ -237,14 +237,14 @@ class Email implements JsonSerializable, Serializable
      * Charset the email header is sent in
      * If null, the $charset property will be used as default
      *
-     * @var string
+     * @var string|null
      */
     public $headerCharset = null;
 
     /**
      * The application wide charset, used to encode headers and body
      *
-     * @var string
+     * @var string|null
      */
     protected $_appCharset = null;
 
@@ -260,7 +260,7 @@ class Email implements JsonSerializable, Serializable
     /**
      * If set, boundary to use for multipart mime messages
      *
-     * @var string
+     * @var string|null
      */
     protected $_boundary = null;
 
diff --git a/src/Mailer/Transport/SmtpTransport.php b/src/Mailer/Transport/SmtpTransport.php
index 433ef1be87b..b830b8dbc8a 100644
--- a/src/Mailer/Transport/SmtpTransport.php
+++ b/src/Mailer/Transport/SmtpTransport.php
@@ -52,9 +52,9 @@ class SmtpTransport extends AbstractTransport
     /**
      * Content of email to return
      *
-     * @var string
+     * @var array
      */
-    protected $_content;
+    protected $_content = [];
 
     /**
      * The response of the last sent SMTP command.
diff --git a/src/Network/Session.php b/src/Network/Session.php
index 97c585ddc1d..8024045a2d6 100644
--- a/src/Network/Session.php
+++ b/src/Network/Session.php
@@ -319,7 +319,7 @@ public function start()
         }
 
         if (ini_get('session.use_cookies') && headers_sent($file, $line)) {
-            return;
+            return false;
         }
 
         if (!session_start()) {
diff --git a/src/Network/Socket.php b/src/Network/Socket.php
index 6d6b42bea2a..30517f43b20 100644
--- a/src/Network/Socket.php
+++ b/src/Network/Socket.php
@@ -53,7 +53,7 @@ class Socket
     /**
      * Reference to socket connection resource
      *
-     * @var resource
+     * @var resource|null
      */
     public $connection = null;
 
@@ -312,8 +312,8 @@ public function setLastError($errNum, $errStr)
     /**
      * Write data to the socket.
      *
-     * @param string $data The data to write to the socket
-     * @return bool Success
+     * @param string $data The data to write to the socket.
+     * @return int Bytes written.
      */
     public function write($data)
     {
diff --git a/src/ORM/Behavior/TimestampBehavior.php b/src/ORM/Behavior/TimestampBehavior.php
index 3b6e5372650..063538b625e 100644
--- a/src/ORM/Behavior/TimestampBehavior.php
+++ b/src/ORM/Behavior/TimestampBehavior.php
@@ -132,7 +132,7 @@ public function implementedEvents()
      *
      * @param \DateTime|null $ts Timestamp
      * @param bool $refreshTimestamp If true timestamp is refreshed.
-     * @return \Cake\I18n\Time
+     * @return \DateTime
      */
     public function timestamp(DateTime $ts = null, $refreshTimestamp = false)
     {
diff --git a/src/ORM/Behavior/TranslateBehavior.php b/src/ORM/Behavior/TranslateBehavior.php
index 59315d8ea00..51eb078a3cc 100644
--- a/src/ORM/Behavior/TranslateBehavior.php
+++ b/src/ORM/Behavior/TranslateBehavior.php
@@ -480,7 +480,7 @@ protected function _referenceName(Table $table)
      *
      * @param \Cake\Datasource\ResultSetInterface $results Results to map.
      * @param string $locale Locale string
-     * @return \Cake\Collection\Collection
+     * @return \Cake\Collection\CollectionInterface
      */
     protected function _rowMapper($results, $locale)
     {
@@ -521,7 +521,7 @@ protected function _rowMapper($results, $locale)
      * into each entity under the `_translations` key
      *
      * @param \Cake\Datasource\ResultSetInterface $results Results to modify.
-     * @return \Cake\Collection\Collection
+     * @return \Cake\Collection\CollectionInterface
      */
     public function groupTranslations($results)
     {
diff --git a/src/ORM/Behavior/TreeBehavior.php b/src/ORM/Behavior/TreeBehavior.php
index 619a6e929c1..1fb89664771 100644
--- a/src/ORM/Behavior/TreeBehavior.php
+++ b/src/ORM/Behavior/TreeBehavior.php
@@ -966,8 +966,8 @@ protected function _ensureFields($entity)
     protected function _getPrimaryKey()
     {
         if (!$this->_primaryKey) {
-            $this->_primaryKey = (array)$this->_table->primaryKey();
-            $this->_primaryKey = $this->_primaryKey[0];
+            $primaryKey = (array)$this->_table->primaryKey();
+            $this->_primaryKey = $primaryKey[0];
         }
 
         return $this->_primaryKey;
diff --git a/src/ORM/EagerLoader.php b/src/ORM/EagerLoader.php
index e2bf54f37f2..055eec82c11 100644
--- a/src/ORM/EagerLoader.php
+++ b/src/ORM/EagerLoader.php
@@ -40,9 +40,9 @@ class EagerLoader
      * Contains a nested array with the compiled containments tree
      * This is a normalized version of the user provided containments array.
      *
-     * @var array
+     * @var \Cake\ORM\EagerLoadable[]|\Cake\ORM\EagerLoadable|null
      */
-    protected $_normalized;
+    protected $_normalized = null;
 
     /**
      * List of options accepted by associations in contain()
@@ -67,7 +67,7 @@ class EagerLoader
     /**
      * A list of associations that should be loaded with a separate query
      *
-     * @var array
+     * @var \Cake\ORM\EagerLoadable[]
      */
     protected $_loadExternal = [];
 
@@ -457,7 +457,7 @@ public function attachableAssociations(Table $repository)
      *
      * @param \Cake\ORM\Table $repository The table containing the associations
      * to be loaded
-     * @return array
+     * @return \Cake\ORM\EagerLoadable[]
      */
     public function externalAssociations(Table $repository)
     {
@@ -481,7 +481,7 @@ public function externalAssociations(Table $repository)
      * separated strings representing associations that lead to this `$alias` in the
      * chain of associations to be loaded. The second value is the path to follow in
      * entities' properties to fetch a record of the corresponding association.
-     * @return array normalized associations
+     * @return \Cake\ORM\EagerLoadable Object with normalized associations
      * @throws \InvalidArgumentException When containments refer to associations that do not exist.
      */
     protected function _normalizeContain(Table $parent, $alias, $options, $paths)
@@ -551,6 +551,7 @@ protected function _fixStrategies()
                 if (count($configs) < 2) {
                     continue;
                 }
+                /* @var \Cake\ORM\EagerLoadable $loadable */
                 foreach ($configs as $loadable) {
                     if (strpos($loadable->aliasPath(), '.')) {
                         $this->_correctStrategy($loadable);
@@ -624,7 +625,7 @@ protected function _resolveJoins($associations, $matching = [])
      * @param \Cake\ORM\Query $query The query for which to eager load external
      * associations
      * @param \Cake\Database\StatementInterface $statement The statement created after executing the $query
-     * @return \Cake\Database\Statement\CallbackStatement statement modified statement with extra loaders
+     * @return \Cake\Database\StatementInterface statement modified statement with extra loaders
      */
     public function loadExternal($query, $statement)
     {
@@ -687,6 +688,7 @@ public function associationsMap($table)
         }
 
         $visitor = function ($level, $matching = false) use (&$visitor, &$map) {
+            /* @var \Cake\ORM\EagerLoadable $meta */
             foreach ($level as $assoc => $meta) {
                 $canBeJoined = $meta->canBeJoined();
                 $instance = $meta->instance();
@@ -750,6 +752,7 @@ public function addToJoinsMap($alias, Association $assoc, $asMatching = false, $
     protected function _collectKeys($external, $query, $statement)
     {
         $collectKeys = [];
+        /* @var \Cake\ORM\EagerLoadable $meta */
         foreach ($external as $meta) {
             $instance = $meta->instance();
             if (!$instance->requiresKeys($meta->config())) {
diff --git a/src/ORM/Query.php b/src/ORM/Query.php
index 62af60447ee..0e19ab778b5 100644
--- a/src/ORM/Query.php
+++ b/src/ORM/Query.php
@@ -148,7 +148,7 @@ class Query extends DatabaseQuery implements JsonSerializable, QueryInterface
      *
      * When set, count query execution will be bypassed.
      *
-     * @var int
+     * @var int|null
      */
     protected $_resultsCount;
 
diff --git a/src/Routing/Dispatcher.php b/src/Routing/Dispatcher.php
index bfb66d3a429..d55f9436ddb 100644
--- a/src/Routing/Dispatcher.php
+++ b/src/Routing/Dispatcher.php
@@ -50,7 +50,7 @@ class Dispatcher
      * If the controller is found, and the action is not found an exception will be thrown.
      *
      * @param \Cake\Http\ServerRequest $request Request object to dispatch.
-     * @param \Cake\Network\Response $response Response object to put the results of the dispatch into.
+     * @param \Cake\Http\Response $response Response object to put the results of the dispatch into.
      * @return string|null if `$request['return']` is set then it returns response body, null otherwise
      * @throws \LogicException When the controller did not get created in the Dispatcher.beforeDispatch event.
      */
diff --git a/src/Routing/DispatcherFilter.php b/src/Routing/DispatcherFilter.php
index b5bd8667890..b7c74a8641b 100644
--- a/src/Routing/DispatcherFilter.php
+++ b/src/Routing/DispatcherFilter.php
@@ -156,6 +156,7 @@ public function handle(Event $event)
      */
     public function matches(Event $event)
     {
+        /* @var \Cake\Http\ServerRequest $request */
         $request = $event->data('request');
         $pass = true;
         if (!empty($this->_config['for'])) {
diff --git a/src/Routing/Filter/AssetFilter.php b/src/Routing/Filter/AssetFilter.php
index 55f9c82b746..d78082f125b 100644
--- a/src/Routing/Filter/AssetFilter.php
+++ b/src/Routing/Filter/AssetFilter.php
@@ -66,6 +66,7 @@ public function __construct($config = [])
      */
     public function beforeDispatch(Event $event)
     {
+        /* @var \Cake\Http\ServerRequest $request */
         $request = $event->data('request');
 
         $url = urldecode($request->url);
@@ -77,6 +78,7 @@ public function beforeDispatch(Event $event)
         if ($assetFile === null || !file_exists($assetFile)) {
             return null;
         }
+        /* @var \Cake\Network\Response $response */
         $response = $event->data('response');
         $event->stopPropagation();
 
diff --git a/src/Routing/Filter/LocaleSelectorFilter.php b/src/Routing/Filter/LocaleSelectorFilter.php
index 4b2cd484740..bf1a82cfe3e 100644
--- a/src/Routing/Filter/LocaleSelectorFilter.php
+++ b/src/Routing/Filter/LocaleSelectorFilter.php
@@ -58,6 +58,7 @@ public function __construct($config = [])
      */
     public function beforeDispatch(Event $event)
     {
+        /* @var \Cake\Http\ServerRequest $request */
         $request = $event->data('request');
         $locale = Locale::acceptFromHttp($request->header('Accept-Language'));
 
diff --git a/src/Routing/Filter/RoutingFilter.php b/src/Routing/Filter/RoutingFilter.php
index 271ad8efb7a..c6e1dc593e3 100644
--- a/src/Routing/Filter/RoutingFilter.php
+++ b/src/Routing/Filter/RoutingFilter.php
@@ -47,6 +47,7 @@ class RoutingFilter extends DispatcherFilter
      */
     public function beforeDispatch(Event $event)
     {
+        /* @var \Cake\Http\ServerRequest $request */
         $request = $event->data('request');
         if (Router::getRequest(true) !== $request) {
             Router::setRequestInfo($request);
@@ -61,6 +62,7 @@ public function beforeDispatch(Event $event)
             return null;
         } catch (RedirectException $e) {
             $event->stopPropagation();
+            /* @var \Cake\Network\Response $response */
             $response = $event->data('response');
             $response->statusCode($e->getCode());
             $response->header('Location', $e->getMessage());
diff --git a/src/Routing/Route/Route.php b/src/Routing/Route/Route.php
index 1223cd34784..43d3dd3f15c 100644
--- a/src/Routing/Route/Route.php
+++ b/src/Routing/Route/Route.php
@@ -163,7 +163,7 @@ public function compiled()
      * Modifies defaults property so all necessary keys are set
      * and populates $this->names with the named routing elements.
      *
-     * @return array Returns a string regular expression of the compiled route.
+     * @return string Returns a string regular expression of the compiled route.
      */
     public function compile()
     {
diff --git a/src/Routing/RouteBuilder.php b/src/Routing/RouteBuilder.php
index 2a886f8d005..2f7a39738c0 100644
--- a/src/Routing/RouteBuilder.php
+++ b/src/Routing/RouteBuilder.php
@@ -189,7 +189,7 @@ public function path()
     /**
      * Get the parameter names/values for this scope.
      *
-     * @return string
+     * @return array
      */
     public function params()
     {
diff --git a/src/Routing/Router.php b/src/Routing/Router.php
index b2a7417eee3..b528abbc7f0 100644
--- a/src/Routing/Router.php
+++ b/src/Routing/Router.php
@@ -45,7 +45,7 @@ class Router
     /**
      * Default route class.
      *
-     * @var bool
+     * @var string
      */
     protected static $_defaultRouteClass = 'Cake\Routing\Route\Route';
 
diff --git a/src/Shell/CommandListShell.php b/src/Shell/CommandListShell.php
index 94d7de6df09..fb96bc127a1 100644
--- a/src/Shell/CommandListShell.php
+++ b/src/Shell/CommandListShell.php
@@ -127,7 +127,7 @@ protected function _asXml($shellList)
             }
         }
         $this->_io->outputAs(ConsoleOutput::RAW);
-        $this->out($shells->saveXml());
+        $this->out($shells->saveXML());
     }
 
     /**
diff --git a/src/Shell/ServerShell.php b/src/Shell/ServerShell.php
index fb25ebb19da..3775b80b7de 100644
--- a/src/Shell/ServerShell.php
+++ b/src/Shell/ServerShell.php
@@ -48,7 +48,7 @@ class ServerShell extends Shell
     /**
      * listen port
      *
-     * @var string
+     * @var int
      */
     protected $_port = null;
 
diff --git a/src/Shell/Task/ExtractTask.php b/src/Shell/Task/ExtractTask.php
index b0d620e6b97..ffdd7fda875 100644
--- a/src/Shell/Task/ExtractTask.php
+++ b/src/Shell/Task/ExtractTask.php
@@ -93,7 +93,7 @@ class ExtractTask extends Shell
     /**
      * Holds the validation string domain to use for validation messages when extracting
      *
-     * @var bool
+     * @var string
      */
     protected $_validationDomain = 'default';
 
diff --git a/src/TestSuite/Fixture/FixtureInjector.php b/src/TestSuite/Fixture/FixtureInjector.php
index e8e7143217d..983d40483e1 100644
--- a/src/TestSuite/Fixture/FixtureInjector.php
+++ b/src/TestSuite/Fixture/FixtureInjector.php
@@ -54,7 +54,7 @@ public function __construct(FixtureManager $manager)
             $manager->setDebug(in_array('--debug', $_SERVER['argv']));
         }
         $this->_fixtureManager = $manager;
-        $this->_fixtureManager->shutdown();
+        $this->_fixtureManager->shutDown();
     }
 
     /**
@@ -81,7 +81,7 @@ public function startTestSuite(PHPUnit_Framework_TestSuite $suite)
     public function endTestSuite(PHPUnit_Framework_TestSuite $suite)
     {
         if ($this->_first === $suite) {
-            $this->_fixtureManager->shutdown();
+            $this->_fixtureManager->shutDown();
         }
     }
 
diff --git a/src/TestSuite/IntegrationTestCase.php b/src/TestSuite/IntegrationTestCase.php
index 6edbb896289..bfcd4688c68 100644
--- a/src/TestSuite/IntegrationTestCase.php
+++ b/src/TestSuite/IntegrationTestCase.php
@@ -54,14 +54,14 @@ abstract class IntegrationTestCase extends TestCase
      *
      * @var string|null
      */
-    protected $_appClass;
+    protected $_appClass = null;
 
     /**
      * The customized application constructor arguments.
      *
      * @var array|null
      */
-    protected $_appArgs;
+    protected $_appArgs = null;
 
     /**
      * The data used to build the next request.
@@ -73,16 +73,16 @@ abstract class IntegrationTestCase extends TestCase
     /**
      * The response for the most recent request.
      *
-     * @var \Cake\Http\Response
+     * @var \Cake\Http\Response|null
      */
-    protected $_response;
+    protected $_response = null;
 
     /**
      * The exception being thrown if the case.
      *
-     * @var \Cake\Core\Exception\Exception
+     * @var \Exception|null
      */
-    protected $_exception;
+    protected $_exception = null;
 
     /**
      * Session data to use in the next request.
@@ -101,30 +101,30 @@ abstract class IntegrationTestCase extends TestCase
     /**
      * The controller used in the last request.
      *
-     * @var \Cake\Controller\Controller
+     * @var \Cake\Controller\Controller|null
      */
-    protected $_controller;
+    protected $_controller = null;
 
     /**
      * The last rendered view
      *
-     * @var string
+     * @var string|null
      */
-    protected $_viewName;
+    protected $_viewName = null;
 
     /**
      * The last rendered layout
      *
-     * @var string
+     * @var string|null
      */
-    protected $_layoutName;
+    protected $_layoutName = null;
 
     /**
      * The session instance from the last request
      *
-     * @var \Cake\Network\Session
+     * @var \Cake\Network\Session|null
      */
-    protected $_requestSession;
+    protected $_requestSession = null;
 
     /**
      * Boolean flag for whether or not the request should have
@@ -435,7 +435,7 @@ protected function _sendRequest($url, $method, $data = [])
     /**
      * Get the correct dispatcher instance.
      *
-     * @return object A dispatcher instance
+     * @return \Cake\TestSuite\MiddlewareDispatcher|\Cake\TestSuite\LegacyRequestDispatcher A dispatcher instance
      */
     protected function _makeDispatcher()
     {
diff --git a/src/TestSuite/MiddlewareDispatcher.php b/src/TestSuite/MiddlewareDispatcher.php
index 145c3fa8c57..7b6b9a896e7 100644
--- a/src/TestSuite/MiddlewareDispatcher.php
+++ b/src/TestSuite/MiddlewareDispatcher.php
@@ -70,7 +70,7 @@ public function __construct($test, $class = null, $constructorArgs = null)
      * Run a request and get the response.
      *
      * @param \Cake\Http\ServerRequest $request The request to execute.
-     * @return \Cake\Http\Response The generated response.
+     * @return \Psr\Http\Message\ResponseInterface The generated response.
      */
     public function execute($request)
     {
diff --git a/src/TestSuite/TestCase.php b/src/TestSuite/TestCase.php
index ee4260e174e..851d8963027 100644
--- a/src/TestSuite/TestCase.php
+++ b/src/TestSuite/TestCase.php
@@ -516,7 +516,7 @@ public function assertHtml($expected, $string, $fullDebug = false)
      * @param string $string The HTML string to check.
      * @param bool $fullDebug Whether or not more verbose output should be used.
      * @param array|string $regex Full regexp from `assertHtml`
-     * @return string
+     * @return string|bool
      */
     protected function _assertAttributes($assertions, $string, $fullDebug = false, $regex = '')
     {
diff --git a/src/Utility/CookieCryptTrait.php b/src/Utility/CookieCryptTrait.php
index 6cdba47bc6e..4af2fec4658 100644
--- a/src/Utility/CookieCryptTrait.php
+++ b/src/Utility/CookieCryptTrait.php
@@ -97,7 +97,7 @@ protected function _checkCipher($encrypt)
      * @param array $values Values to decrypt
      * @param string|bool $mode Encryption mode
      * @param string|null $key Used as the security salt if specified.
-     * @return string decrypted string
+     * @return string|array Decrypted values
      */
     protected function _decrypt($values, $mode, $key = null)
     {
@@ -119,7 +119,7 @@ protected function _decrypt($values, $mode, $key = null)
      * @param string $value The value to decode & decrypt.
      * @param string|false $encrypt The encryption cipher to use.
      * @param string|null $key Used as the security salt if specified.
-     * @return string Decoded value.
+     * @return string|array Decoded values.
      */
     protected function _decode($value, $encrypt, $key)
     {
@@ -158,7 +158,7 @@ protected function _implode(array $array)
      * Maintains reading backwards compatibility with 1.x CookieComponent::_implode().
      *
      * @param string $string A string containing JSON encoded data, or a bare string.
-     * @return array Map of key and values
+     * @return string|array Map of key and values
      */
     protected function _explode($string)
     {
diff --git a/src/Utility/Security.php b/src/Utility/Security.php
index 242f19039cf..00144c1c80c 100644
--- a/src/Utility/Security.php
+++ b/src/Utility/Security.php
@@ -255,7 +255,7 @@ protected static function _checkKey($key, $method)
      * @param string $cipher The ciphertext to decrypt.
      * @param string $key The 256 bit/32 byte key to use as a cipher key.
      * @param string|null $hmacSalt The salt to use for the HMAC process. Leave null to use Security.salt.
-     * @return string Decrypted data. Any trailing null bytes will be removed.
+     * @return string|bool Decrypted data. Any trailing null bytes will be removed.
      * @throws \InvalidArgumentException On invalid data or key.
      */
     public static function decrypt($cipher, $key, $hmacSalt = null)
diff --git a/src/View/Form/EntityContext.php b/src/View/Form/EntityContext.php
index fbb09d65fd4..2b3dbe29817 100644
--- a/src/View/Form/EntityContext.php
+++ b/src/View/Form/EntityContext.php
@@ -295,7 +295,7 @@ protected function _schemaDefault($field, $entity)
      *
      * @param array|\Traversable $values The list from which to extract primary keys from
      * @param array $path Each one of the parts in a path for a field name
-     * @return array
+     * @return array|null
      */
     protected function _extractMultiple($values, $path)
     {
diff --git a/src/View/Helper/FormHelper.php b/src/View/Helper/FormHelper.php
index e78385fea6b..a7795a0302c 100644
--- a/src/View/Helper/FormHelper.php
+++ b/src/View/Helper/FormHelper.php
@@ -161,7 +161,7 @@ class FormHelper extends Helper
     /**
      * Defines the type of form being created. Set by FormHelper::create().
      *
-     * @var string
+     * @var string|null
      */
     public $requestType = null;
 
@@ -185,7 +185,7 @@ class FormHelper extends Helper
     /**
      * Context for the current form.
      *
-     * @var \Cake\View\Form\ContextInterface
+     * @var \Cake\View\Form\ContextInterface|null
      */
     protected $_context;
 
@@ -689,7 +689,9 @@ protected function _secure($lock, $field, $value = null)
         if ($lock) {
             if (!in_array($field, $this->fields)) {
                 if ($value !== null) {
-                    return $this->fields[$field] = $value;
+                    $this->fields[$field] = $value;
+
+                    return;
                 }
                 if (isset($this->fields[$field]) && $value === null) {
                     unset($this->fields[$field]);
diff --git a/src/View/Helper/HtmlHelper.php b/src/View/Helper/HtmlHelper.php
index e0ed36c2b83..673411b60dc 100644
--- a/src/View/Helper/HtmlHelper.php
+++ b/src/View/Helper/HtmlHelper.php
@@ -924,6 +924,7 @@ public function tableCells($data, $oddTrOptions = null, $evenTrOptions = null, $
             $count = 0;
         }
 
+        $out = [];
         foreach ($data as $line) {
             $count++;
             $cellsOut = $this->_renderCells($line, $useCount);
@@ -942,7 +943,7 @@ public function tableCells($data, $oddTrOptions = null, $evenTrOptions = null, $
      *
      * @param array $line Line data to render.
      * @param bool $useCount Renders the count into the row. Default is false.
-     * @return string
+     * @return string[]
      */
     protected function _renderCells($line, $useCount = false)
     {
diff --git a/src/View/Helper/NumberHelper.php b/src/View/Helper/NumberHelper.php
index 738c6027049..2f1c5ea8d0a 100644
--- a/src/View/Helper/NumberHelper.php
+++ b/src/View/Helper/NumberHelper.php
@@ -89,7 +89,7 @@ public function __call($method, $params)
      *
      * @param float $number A floating point number.
      * @param int $precision The precision of the returned number.
-     * @return float Formatted float.
+     * @return string Formatted float.
      * @see \Cake\I18n\Number::precision()
      * @link http://book.cakephp.org/3.0/en/views/helpers/number.html#formatting-floating-point-numbers
      */
diff --git a/src/View/Helper/PaginatorHelper.php b/src/View/Helper/PaginatorHelper.php
index 6f9f64cdb25..5db4e3bc993 100644
--- a/src/View/Helper/PaginatorHelper.php
+++ b/src/View/Helper/PaginatorHelper.php
@@ -746,7 +746,7 @@ public function counter($options = [])
      * options and a modulus of 8, ellipsis content will be inserted after the first and last link sets.
      *
      * @param array $options Options for the numbers.
-     * @return string numbers string.
+     * @return string|false Numbers string.
      * @link http://book.cakephp.org/3.0/en/views/helpers/paginator.html#creating-page-number-links
      */
     public function numbers(array $options = [])
@@ -987,7 +987,7 @@ protected function _numbers($templater, $params, $options)
      * @param string|int $first if string use as label for the link. If numeric, the number of page links
      *   you want at the beginning of the range.
      * @param array $options An array of options.
-     * @return string numbers string.
+     * @return string|false Numbers string.
      * @link http://book.cakephp.org/3.0/en/views/helpers/paginator.html#creating-jump-links
      */
     public function first($first = '<< first', array $options = [])
@@ -1048,7 +1048,7 @@ public function first($first = '<< first', array $options = [])
      *
      * @param string|int $last if string use as label for the link, if numeric print page numbers
      * @param array $options Array of options
-     * @return string numbers string.
+     * @return string|false Numbers string.
      * @link http://book.cakephp.org/3.0/en/views/helpers/paginator.html#creating-jump-links
      */
     public function last($last = 'last >>', array $options = [])
diff --git a/src/View/Helper/TimeHelper.php b/src/View/Helper/TimeHelper.php
index 3bb209a3300..360fcaeac70 100644
--- a/src/View/Helper/TimeHelper.php
+++ b/src/View/Helper/TimeHelper.php
@@ -205,7 +205,7 @@ public function toQuarter($dateString, $range = false)
      */
     public function toUnix($dateString, $timezone = null)
     {
-        return (new Time($dateString, $timezone))->toUnixString();
+        return (int)(new Time($dateString, $timezone))->toUnixString();
     }
 
     /**
@@ -334,7 +334,7 @@ public function isWithinNext($timeInterval, $dateString, $timezone = null)
      */
     public function gmt($string = null)
     {
-        return (new Time($string))->toUnixString();
+        return (int)(new Time($string))->toUnixString();
     }
 
     /**
diff --git a/src/View/SerializedView.php b/src/View/SerializedView.php
index 6f07e2a68d3..0218f65b370 100644
--- a/src/View/SerializedView.php
+++ b/src/View/SerializedView.php
@@ -83,7 +83,7 @@ abstract protected function _serialize($serialize);
      *   names. If true all view variables will be serialized. If unset normal
      *   view template will be rendered.
      *
-     * @param string|null $view The view being rendered.
+     * @param string|bool|null $view The view being rendered.
      * @param string|null $layout The layout being rendered.
      * @return string|null The rendered view.
      */
diff --git a/src/View/View.php b/src/View/View.php
index 0e0071777e9..c66529aada1 100644
--- a/src/View/View.php
+++ b/src/View/View.php
@@ -568,7 +568,7 @@ public function elementExists($name)
      * a plugin template/layout can be used instead of the app ones. If the chosen plugin is not found
      * the template will be located along the regular view path cascade.
      *
-     * @param string|null $view Name of view file to use
+     * @param string|false|null $view Name of view file to use
      * @param string|null $layout Layout to use.
      * @return string|null Rendered content or null if content already rendered and returned earlier.
      * @throws \Cake\Core\Exception\Exception If there is an error in the view.
diff --git a/src/View/Widget/MultiCheckboxWidget.php b/src/View/Widget/MultiCheckboxWidget.php
index f417522a404..9b1ac7d885c 100644
--- a/src/View/Widget/MultiCheckboxWidget.php
+++ b/src/View/Widget/MultiCheckboxWidget.php
@@ -236,7 +236,7 @@ protected function _isSelected($key, $selected)
      * Helper method for deciding what options are disabled.
      *
      * @param string $key The key to test.
-     * @param array|null $disabled The disabled values.
+     * @param array|bool|null $disabled The disabled values.
      * @return bool
      */
     protected function _isDisabled($key, $disabled)
diff --git a/src/View/Widget/RadioWidget.php b/src/View/Widget/RadioWidget.php
index e91cf570b84..bb5e2d7d774 100644
--- a/src/View/Widget/RadioWidget.php
+++ b/src/View/Widget/RadioWidget.php
@@ -222,7 +222,7 @@ protected function _renderInput($val, $text, $data, $context)
      * @param string $input The input widget.
      * @param \Cake\View\Form\ContextInterface $context The form context.
      * @param bool $escape Whether or not to HTML escape the label.
-     * @return string Generated label.
+     * @return string|bool Generated label.
      */
     protected function _renderLabel($radio, $label, $input, $context, $escape)
     {
diff --git a/tests/TestCase/Controller/Component/CookieComponentTest.php b/tests/TestCase/Controller/Component/CookieComponentTest.php
index d2f25379719..39d0dff3067 100644
--- a/tests/TestCase/Controller/Component/CookieComponentTest.php
+++ b/tests/TestCase/Controller/Component/CookieComponentTest.php
@@ -28,6 +28,11 @@
 class CookieComponentTest extends TestCase
 {
 
+    /**
+     * @var \Cake\Controller\Component\CookieComponent
+     */
+    protected $Cookie;
+
     /**
      * start
      *
diff --git a/tests/TestCase/Database/DriverTest.php b/tests/TestCase/Database/DriverTest.php
index 94cf116962e..2504c3ecf7d 100644
--- a/tests/TestCase/Database/DriverTest.php
+++ b/tests/TestCase/Database/DriverTest.php
@@ -261,7 +261,7 @@ public function schemaValueProvider()
             [null, 'NULL'],
             [false, 'FALSE'],
             [true, 'TRUE'],
-            [1, 1],
+            [1, '1'],
             ['0', '0'],
             ['42', '42']
         ];
diff --git a/tests/TestCase/Database/Type/FloatTypeTest.php b/tests/TestCase/Database/Type/FloatTypeTest.php
index 62eb5c7d472..83d83696cff 100644
--- a/tests/TestCase/Database/Type/FloatTypeTest.php
+++ b/tests/TestCase/Database/Type/FloatTypeTest.php
@@ -92,7 +92,7 @@ public function testToPHP()
         $this->assertSame(2.0, $result);
 
         $result = $this->type->toPHP(['3', '4'], $this->driver);
-        $this->assertSame(1, $result);
+        $this->assertSame(1.0, $result);
     }
 
     /**
@@ -141,7 +141,7 @@ public function testMarshal()
         $this->assertSame('3.5 bears', $result);
 
         $result = $this->type->marshal(['3', '4']);
-        $this->assertSame(1, $result);
+        $this->assertSame(1.0, $result);
     }
 
     /**
diff --git a/tests/TestCase/View/Helper/TimeHelperTest.php b/tests/TestCase/View/Helper/TimeHelperTest.php
index 0400a5cdb59..ce1382251e4 100644
--- a/tests/TestCase/View/Helper/TimeHelperTest.php
+++ b/tests/TestCase/View/Helper/TimeHelperTest.php
@@ -183,7 +183,7 @@ public function testNiceOutputTimezone()
      */
     public function testToUnix()
     {
-        $this->assertEquals(1397980800, $this->Time->toUnix('2014-04-20 08:00:00'));
+        $this->assertSame(1397980800, $this->Time->toUnix('2014-04-20 08:00:00'));
     }
 
     /**