diff --git a/src/CookieCollection.php b/src/CookieCollection.php
index aa2f102c9..910cac0a3 100644
--- a/src/CookieCollection.php
+++ b/src/CookieCollection.php
@@ -13,6 +13,8 @@
 use IteratorAggregate;
 use Psr\Http\Message\ResponseInterface;
 
+use Yiisoft\Http\Header;
+
 use function array_keys;
 use function array_values;
 use function array_walk;
@@ -34,7 +36,7 @@ final class CookieCollection implements IteratorAggregate, ArrayAccess, Countabl
     /**
      * CookieCollection constructor.
      *
-     * @param array $cookies the cookies that this collection initially contains.
+     * @param Cookie[] $cookies the cookies that this collection initially contains.
      */
     public function __construct(array $cookies = [])
     {
@@ -339,7 +341,7 @@ public function addToResponse(ResponseInterface $response): ResponseInterface
      */
     public function setToResponse(ResponseInterface $response): ResponseInterface
     {
-        $response = $response->withoutHeader('Set-Cookie');
+        $response = $response->withoutHeader(Header::SET_COOKIE);
         return $this->addToResponse($response);
     }
 
@@ -353,7 +355,7 @@ public function setToResponse(ResponseInterface $response): ResponseInterface
     public static function fromResponse(ResponseInterface $response): self
     {
         $collection = new self();
-        foreach ($response->getHeader('Set-Cookie') as $setCookieString) {
+        foreach ($response->getHeader(Header::SET_COOKIE) as $setCookieString) {
             $cookie = Cookie::fromCookieString($setCookieString);
             $collection->add($cookie);
         }
diff --git a/src/Data/Formatter/HtmlDataResponseFormatter.php b/src/Data/Formatter/HtmlDataResponseFormatter.php
index 5028dd31c..99d000f67 100644
--- a/src/Data/Formatter/HtmlDataResponseFormatter.php
+++ b/src/Data/Formatter/HtmlDataResponseFormatter.php
@@ -5,6 +5,7 @@
 namespace Yiisoft\Yii\Web\Data\Formatter;
 
 use Psr\Http\Message\ResponseInterface;
+use Yiisoft\Http\Header;
 use Yiisoft\Yii\Web\Data\DataResponse;
 use Yiisoft\Yii\Web\Data\DataResponseFormatterInterface;
 
@@ -26,7 +27,7 @@ public function format(DataResponse $dataResponse): ResponseInterface
         $response = $dataResponse->getResponse();
         $response->getBody()->write((string)$data);
 
-        return $response->withHeader('Content-Type', $this->contentType . '; charset=' . $this->encoding);
+        return $response->withHeader(Header::CONTENT_TYPE, $this->contentType . '; charset=' . $this->encoding);
     }
 
     public function withEncoding(string $encoding): self
diff --git a/src/Data/Formatter/JsonDataResponseFormatter.php b/src/Data/Formatter/JsonDataResponseFormatter.php
index 82dfb2403..61be23eb9 100644
--- a/src/Data/Formatter/JsonDataResponseFormatter.php
+++ b/src/Data/Formatter/JsonDataResponseFormatter.php
@@ -5,6 +5,7 @@
 namespace Yiisoft\Yii\Web\Data\Formatter;
 
 use Psr\Http\Message\ResponseInterface;
+use Yiisoft\Http\Header;
 use Yiisoft\Serializer\JsonSerializer;
 use Yiisoft\Yii\Web\Data\DataResponse;
 use Yiisoft\Yii\Web\Data\DataResponseFormatterInterface;
@@ -25,7 +26,7 @@ public function format(DataResponse $dataResponse): ResponseInterface
         $response = $dataResponse->getResponse();
         $response->getBody()->write($content);
 
-        return $response->withHeader('Content-Type', $this->contentType);
+        return $response->withHeader(Header::CONTENT_TYPE, $this->contentType);
     }
 
     public function withOptions(int $options): self
diff --git a/src/Data/Formatter/XmlDataResponseFormatter.php b/src/Data/Formatter/XmlDataResponseFormatter.php
index a40cf0130..17e27c699 100644
--- a/src/Data/Formatter/XmlDataResponseFormatter.php
+++ b/src/Data/Formatter/XmlDataResponseFormatter.php
@@ -9,6 +9,7 @@
 use DOMException;
 use DOMText;
 use Psr\Http\Message\ResponseInterface;
+use Yiisoft\Http\Header;
 use Yiisoft\Strings\StringHelper;
 use Yiisoft\Yii\Web\Data\DataResponse;
 use Yiisoft\Yii\Web\Data\DataResponseFormatterInterface;
@@ -63,7 +64,7 @@ public function format(DataResponse $dataResponse): ResponseInterface
         $response = $dataResponse->getResponse();
         $response->getBody()->write($content);
 
-        return $response->withHeader('Content-Type', $this->contentType . '; ' . $this->encoding);
+        return $response->withHeader(Header::CONTENT_TYPE, $this->contentType . '; ' . $this->encoding);
     }
 
     public function withVersion(string $version): self
diff --git a/src/ErrorHandler/ErrorCatcher.php b/src/ErrorHandler/ErrorCatcher.php
index 4886d3777..ac1b6fb53 100644
--- a/src/ErrorHandler/ErrorCatcher.php
+++ b/src/ErrorHandler/ErrorCatcher.php
@@ -10,12 +10,13 @@
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Server\MiddlewareInterface;
 use Psr\Http\Server\RequestHandlerInterface;
+use Yiisoft\Http\Header;
 use Yiisoft\Http\HeaderHelper;
 use Yiisoft\Http\Status;
 
 /**
  * ErrorCatcher catches all throwables from the next middlewares and renders it
- * accoring to the content type passed by the client.
+ * according to the content type passed by the client.
  */
 final class ErrorCatcher implements MiddlewareInterface
 {
@@ -83,7 +84,7 @@ private function handleException(\Throwable $e, ServerRequestInterface $request)
         }
         $content = $this->errorHandler->handleCaughtThrowable($e, $renderer);
         $response = $this->responseFactory->createResponse(Status::INTERNAL_SERVER_ERROR)
-            ->withHeader('Content-type', $contentType);
+            ->withHeader(Header::CONTENT_TYPE, $contentType);
         $response->getBody()->write($content);
         return $response;
     }
diff --git a/src/ErrorHandler/HtmlRenderer.php b/src/ErrorHandler/HtmlRenderer.php
index e98a6b5bc..06ef60399 100644
--- a/src/ErrorHandler/HtmlRenderer.php
+++ b/src/ErrorHandler/HtmlRenderer.php
@@ -19,12 +19,9 @@ final class HtmlRenderer extends ThrowableRenderer
     private string $errorTemplate;
     private string $exceptionTemplate;
 
-    private array $defaultTemplates;
-
     public function __construct(array $templates = [])
     {
         $this->defaultTemplatePath = $templates['path'];
-        $this->defaultTemplates = $templates['default'];
         $this->errorTemplate = $templates['error'] ?? $this->defaultTemplatePath . '/error.php';
         $this->exceptionTemplate = $templates['exception'] ?? $this->defaultTemplatePath . '/exception.php';
     }
diff --git a/src/ErrorHandler/XmlRenderer.php b/src/ErrorHandler/XmlRenderer.php
index b9be01ca6..770c9d098 100644
--- a/src/ErrorHandler/XmlRenderer.php
+++ b/src/ErrorHandler/XmlRenderer.php
@@ -24,9 +24,9 @@ public function renderVerbose(\Throwable $t): string
         $out .= "<error>\n";
         $out .= $this->tag('type', get_class($t));
         $out .= $this->tag('message', $this->cdata($t->getMessage()));
-        $out .= $this->tag('code', $this->cdata($t->getCode()));
+        $out .= $this->tag('code', $this->cdata((string) $t->getCode()));
         $out .= $this->tag('file', $t->getFile());
-        $out .= $this->tag('line', $t->getLine());
+        $out .= $this->tag('line', (string) $t->getLine());
         $out .= $this->tag('trace', $t->getTraceAsString());
         $out .= '</error>';
         return $out;
diff --git a/src/ErrorHandler/templates/error.php b/src/ErrorHandler/templates/error.php
index ede0d0bf8..94b2fdee5 100644
--- a/src/ErrorHandler/templates/error.php
+++ b/src/ErrorHandler/templates/error.php
@@ -13,7 +13,7 @@
 }
 ?>
 <!DOCTYPE html>
-<html>
+<html lang="en">
 <head>
     <meta charset="utf-8" />
     <title><?= $this->htmlEncode($name) ?></title>
diff --git a/src/ErrorHandler/templates/exception.php b/src/ErrorHandler/templates/exception.php
index 0aefd87ca..75bd4719d 100644
--- a/src/ErrorHandler/templates/exception.php
+++ b/src/ErrorHandler/templates/exception.php
@@ -17,7 +17,6 @@
     margin: 0;
     padding: 0;
     border: 0;
-    font-size: 100%;
     font: inherit;
     vertical-align: baseline;
 }
diff --git a/src/ErrorHandler/templates/previousException.php b/src/ErrorHandler/templates/previousException.php
index c8a6008d0..f566ca850 100644
--- a/src/ErrorHandler/templates/previousException.php
+++ b/src/ErrorHandler/templates/previousException.php
@@ -1,4 +1,5 @@
 <?php
+/* @var $throwable \Throwable */
 /* @var $this \Yiisoft\Yii\Web\ErrorHandler\HtmlRenderer */
 ?>
 <div class="previous">
diff --git a/src/Middleware/ForceSecureConnection.php b/src/Middleware/ForceSecureConnection.php
index 904d00246..76bcabaa8 100644
--- a/src/Middleware/ForceSecureConnection.php
+++ b/src/Middleware/ForceSecureConnection.php
@@ -46,6 +46,7 @@ public function __construct(ResponseFactoryInterface $responseFactory)
     {
         $this->responseFactory = $responseFactory;
     }
+
     public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
     {
         if ($this->redirect && strcasecmp($request->getUri()->getScheme(), 'http') === 0) {
diff --git a/src/Middleware/HttpCache.php b/src/Middleware/HttpCache.php
index b27bead69..244f85a58 100644
--- a/src/Middleware/HttpCache.php
+++ b/src/Middleware/HttpCache.php
@@ -4,11 +4,11 @@
 
 namespace Yiisoft\Yii\Web\Middleware;
 
-use Psr\Http\Message\ResponseFactoryInterface;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Server\MiddlewareInterface;
 use Psr\Http\Server\RequestHandlerInterface;
+use Yiisoft\Http\Header;
 use Yiisoft\Http\Method;
 use Yiisoft\Http\Status;
 
@@ -68,13 +68,6 @@ final class HttpCache implements MiddlewareInterface
      */
     private ?string $cacheControlHeader = self::DEFAULT_HEADER;
 
-    private ResponseFactoryInterface $responseFactory;
-
-    public function __construct(ResponseFactoryInterface $responseFactory)
-    {
-        $this->responseFactory = $responseFactory;
-    }
-
     public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
     {
         if (
@@ -105,16 +98,16 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
         }
 
         if ($this->cacheControlHeader !== null) {
-            $response = $response->withHeader('Cache-Control', $this->cacheControlHeader);
+            $response = $response->withHeader(Header::CACHE_CONTROL, $this->cacheControlHeader);
         }
         if ($etag !== null) {
-            $response = $response->withHeader('Etag', $etag);
+            $response = $response->withHeader(Header::ETAG, $etag);
         }
 
         // https://tools.ietf.org/html/rfc7232#section-4.1
-        if ($lastModified !== null && (!$cacheIsValid || ($cacheIsValid && $etag === null))) {
+        if ($lastModified !== null && (!$cacheIsValid || $etag === null)) {
             $response = $response->withHeader(
-                'Last-Modified',
+                Header::LAST_MODIFIED,
                 gmdate('D, d M Y H:i:s', $lastModified) . ' GMT'
             );
         }
@@ -133,14 +126,14 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
      */
     private function validateCache(ServerRequestInterface $request, ?int $lastModified, ?string $etag): bool
     {
-        if ($request->hasHeader('If-None-Match')) {
+        if ($request->hasHeader(Header::IF_NONE_MATCH)) {
             // HTTP_IF_NONE_MATCH takes precedence over HTTP_IF_MODIFIED_SINCE
             // http://tools.ietf.org/html/rfc7232#section-3.3
             return $etag !== null && \in_array($etag, $this->getETags($request), true);
         }
 
-        if ($request->hasHeader('If-Modified-Since')) {
-            $header = $request->getHeaderLine('If-Modified-Since');
+        if ($request->hasHeader(Header::IF_MODIFIED_SINCE)) {
+            $header = $request->getHeaderLine(Header::IF_MODIFIED_SINCE);
             return $lastModified !== null && @strtotime($header) >= $lastModified;
         }
 
@@ -166,8 +159,8 @@ private function generateEtag(string $seed): string
      */
     private function getETags(ServerRequestInterface $request): array
     {
-        if ($request->hasHeader('If-None-Match')) {
-            $header = $request->getHeaderLine('If-None-Match');
+        if ($request->hasHeader(Header::IF_NONE_MATCH)) {
+            $header = $request->getHeaderLine(Header::IF_NONE_MATCH);
             $header = \str_replace('-gzip', '', $header);
             return \preg_split('/[\s,]+/', $header, -1, PREG_SPLIT_NO_EMPTY) ?: [];
         }
diff --git a/src/Middleware/TrustedHostsNetworkResolver.php b/src/Middleware/TrustedHostsNetworkResolver.php
index 4a1def917..32eb03b68 100644
--- a/src/Middleware/TrustedHostsNetworkResolver.php
+++ b/src/Middleware/TrustedHostsNetworkResolver.php
@@ -5,7 +5,6 @@
 namespace Yiisoft\Yii\Web\Middleware;
 
 use Psr\Http\Message\RequestInterface;
-use Psr\Http\Message\ResponseFactoryInterface;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Server\MiddlewareInterface;
@@ -70,15 +69,8 @@ final class TrustedHostsNetworkResolver implements MiddlewareInterface
 
     private ?string $attributeIps = null;
 
-    private ResponseFactoryInterface $responseFactory;
-
     private ?Ip $ipValidator = null;
 
-    public function __construct(ResponseFactoryInterface $responseFactory)
-    {
-        $this->responseFactory = $responseFactory;
-    }
-
     public function withIpValidator(Ip $ipValidator): self
     {
         $new = clone $this;
diff --git a/src/NotFoundHandler.php b/src/NotFoundHandler.php
index 4ffd7dbab..ef92820e7 100644
--- a/src/NotFoundHandler.php
+++ b/src/NotFoundHandler.php
@@ -15,7 +15,7 @@ final class NotFoundHandler implements RequestHandlerInterface
     /**
      * @var ResponseFactoryInterface
      */
-    private $responseFactory;
+    private ResponseFactoryInterface $responseFactory;
 
     /**
      * NotFoundHandler constructor.
diff --git a/src/ServerRequestFactory.php b/src/ServerRequestFactory.php
index 3e9df1f0c..1772608d6 100644
--- a/src/ServerRequestFactory.php
+++ b/src/ServerRequestFactory.php
@@ -107,7 +107,7 @@ private function getUri(array $server): UriInterface
         }
 
         if (isset($server['HTTP_HOST'])) {
-            if (1 === \preg_match('/^(.+)\:(\d+)$/', $server['HTTP_HOST'], $matches)) {
+            if (1 === \preg_match('/^(.+):(\d+)$/', $server['HTTP_HOST'], $matches)) {
                 $uri = $uri->withHost($matches[1])->withPort($matches[2]);
             } else {
                 $uri = $uri->withHost($server['HTTP_HOST']);
diff --git a/src/Session/SessionInterface.php b/src/Session/SessionInterface.php
index 848a77dd4..73f7374de 100644
--- a/src/Session/SessionInterface.php
+++ b/src/Session/SessionInterface.php
@@ -29,7 +29,7 @@ public function set(string $key, $value): void;
     public function close(): void;
 
     /**
-     * Start sesion if it is not started yet
+     * Start session if it is not started yet
      */
     public function open(): void;
 
diff --git a/src/Session/SessionMiddleware.php b/src/Session/SessionMiddleware.php
index c7d365b57..8ed1a37a9 100644
--- a/src/Session/SessionMiddleware.php
+++ b/src/Session/SessionMiddleware.php
@@ -46,7 +46,7 @@ private function commitSession(ServerRequestInterface $request, ResponseInterfac
 
         $currentSid = $this->session->getID();
 
-        // SID changed, neeed to send new cookie
+        // SID changed, need to send new cookie
         if ($this->getSidFromRequest($request) !== $currentSid) {
             $cookieParameters = $this->session->getCookieParameters();
 
diff --git a/src/User/User.php b/src/User/User.php
index 88e7ebc4d..694e68e5d 100644
--- a/src/User/User.php
+++ b/src/User/User.php
@@ -20,6 +20,19 @@ class User
     private const SESSION_AUTH_EXPIRE = '__auth_expire';
     private const SESSION_AUTH_ABSOLUTE_EXPIRE = '__auth_absolute_expire';
 
+    /**
+     * @var int|null the number of seconds in which the user will be logged out automatically in case of
+     * remaining inactive. If this property is not set, the user will be logged out after
+     * the current session expires.
+     */
+    public ?int $authTimeout = null;
+
+    /**
+     * @var int|null the number of seconds in which the user will be logged out automatically
+     * regardless of activity.
+     */
+    public ?int $absoluteAuthTimeout = null;
+
     private IdentityRepositoryInterface $identityRepository;
     private EventDispatcherInterface $eventDispatcher;
 
@@ -44,19 +57,6 @@ public function __construct(
         $this->session = $session;
     }
 
-    /**
-     * @var int|null the number of seconds in which the user will be logged out automatically if he
-     * remains inactive. If this property is not set, the user will be logged out after
-     * the current session expires.
-     */
-    public ?int $authTimeout = null;
-
-    /**
-     * @var int|null the number of seconds in which the user will be logged out automatically
-     * regardless of activity.
-     */
-    public ?int $absoluteAuthTimeout = null;
-
     public function setAccessChecker(AccessCheckerInterface $accessChecker): void
     {
         $this->accessChecker = $accessChecker;
@@ -72,7 +72,7 @@ public function setAccessChecker(AccessCheckerInterface $accessChecker): void
      * @see logout()
      * @see login()
      */
-    public function getIdentity($autoRenew = true): IdentityInterface
+    public function getIdentity(bool $autoRenew = true): IdentityInterface
     {
         if ($this->identity !== null) {
             return $this->identity;
@@ -151,7 +151,7 @@ public function loginByAccessToken(string $token, string $type = null): ?Identit
      * @return bool whether the user is logged out
      * @throws \Throwable
      */
-    public function logout($destroySession = true): bool
+    public function logout(bool $destroySession = true): bool
     {
         $identity = $this->getIdentity();
         if ($this->isGuest()) {