new-features.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->

<sect1 xml:id="migration70.new-features" xmlns:xlink="http://www.w3.org/1999/xlink">
 <title>New features</title>

 <sect2 xml:id="migration70.new-features.scalar-type-declarations">
  <title>Scalar type declarations</title>

  <para>
   Scalar
   <link linkend="language.types.declarations">type declarations</link>
   come in two flavours: coercive (default) and strict. The following types
   for parameters can now be enforced (either coercively or strictly): strings
    (<type>string</type>), integers (<literal>int</literal>), floating-point
    numbers (<type>float</type>), and booleans (<literal>bool</literal>). They
    augment the other types introduced in PHP 5: class names, interfaces,
    <type>array</type> and <type>callable</type>.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
// Coercive mode
function sumOfInts(int ...$ints)
{
    return array_sum($ints);
}

var_dump(sumOfInts(2, '3', 4.1));
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
int(9)
]]>
   </screen>
  </informalexample>

  <para>
   To enable strict mode, a single &declare; directive must be placed at the
   top of the file. This means that the strictness of typing for scalars is
   configured on a per-file basis. This directive not only affects the type
   declarations of parameters, but also a function's return type (see
   <link linkend="language.types.declarations">return type declarations</link>,
   built-in PHP functions, and functions from loaded
   extensions.
  </para>

  <para>
   Full documentation and examples of scalar type declarations can be found in
   the
   <link linkend="language.types.declarations">type declaration</link>
   reference.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.return-type-declarations">
  <title>Return type declarations</title>

  <para>
   PHP 7 adds support for 
   <link linkend="language.types.declarations">return type declarations</link>.
   Similarly to
   <link linkend="language.types.declarations">argument type declarations</link>,
   return type declarations specify the type of the value that will be
   returned from a function. The same
   <link linkend="language.types.declarations">types</link>
   are available for return type declarations as are available for argument
   type declarations.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php

function arraysSum(array ...$arrays): array
{
    return array_map(function(array $array): int {
        return array_sum($array);
    }, $arrays);
}

print_r(arraysSum([1,2,3], [4,5,6], [7,8,9]));
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
Array
(
    [0] => 6
    [1] => 15
    [2] => 24
)
]]>
   </screen>
  </informalexample>

  <para>
   Full documentation and examples of return type declarations can be found in
   the
   <link linkend="language.types.declarations">return type declarations</link>.
   reference.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.null-coalesce-op">
  <title>Null coalescing operator</title>

  <para>
   The null coalescing operator (<literal>??</literal>) has been added as
   syntactic sugar for the common case of needing to use a ternary in
   conjunction with <function>isset</function>. It returns its first operand
   if it exists and is not &null;; otherwise it returns its second operand.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
// Fetches the value of $_GET['user'] and returns 'nobody'
// if it does not exist.
$username = $_GET['user'] ?? 'nobody';
// This is equivalent to:
$username = isset($_GET['user']) ? $_GET['user'] : 'nobody';

// Coalescing can be chained: this will return the first
// defined value out of $_GET['user'], $_POST['user'], and
// 'nobody'.
$username = $_GET['user'] ?? $_POST['user'] ?? 'nobody';
?>
]]>
   </programlisting>
  </informalexample>

  <!-- TODO: we don't need further details here, but this still has to be
       added to the operator precedence table -->
 </sect2>

 <sect2 xml:id="migration70.new-features.spaceship-op">
  <title>Spaceship operator</title>
  <para>
   The spaceship operator is used for comparing two expressions. It returns -1, 0 
   or 1 when <varname>$a</varname> is respectively less than, equal to, or greater 
   than <varname>$b</varname>. Comparisons are performed according to PHP's usual
   <link linkend="types.comparisons">type comparison rules</link>.
  </para>
  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
// Integers
echo 1 <=> 1; // 0
echo 1 <=> 2; // -1
echo 2 <=> 1; // 1

// Floats
echo 1.5 <=> 1.5; // 0
echo 1.5 <=> 2.5; // -1
echo 2.5 <=> 1.5; // 1
 
// Strings
echo "a" <=> "a"; // 0
echo "a" <=> "b"; // -1
echo "b" <=> "a"; // 1
?>
]]>
   </programlisting>
  </informalexample>

  <!-- TODO: we don't need further details here, but this still has to be
       added to the operator precedence table -->
 </sect2>

 <sect2 xml:id="migration70.new-features.define-array">
  <title>Constant arrays using <function>define</function></title>

  <para>
   <type>Array</type> constants can now be defined with
   <function>define</function>. In PHP 5.6, they could only be defined with
   &const;.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
define('ANIMALS', [
    'dog',
    'cat',
    'bird'
]);

echo ANIMALS[1]; // outputs "cat"
?>
]]>
   </programlisting>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.anonymous-classes">
  <title>Anonymous classes</title>

  <para>
   Support for anonymous classes has been added via <literal>new
   class</literal>. These can be used in place of full class definitions for
   throwaway objects:
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
interface Logger {
    public function log(string $msg);
}

class Application {
    private $logger;

    public function getLogger(): Logger {
         return $this->logger;
    }

    public function setLogger(Logger $logger) {
         $this->logger = $logger;
    }
}

$app = new Application;
$app->setLogger(new class implements Logger {
    public function log(string $msg) {
        echo $msg;
    }
});

var_dump($app->getLogger());
?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
object(class@anonymous)#2 (0) {
}
]]>
   </screen>
  </informalexample>

  <para>
   Full documentation can be found in the 
   <link linkend="language.oop5.anonymous">anonymous class reference</link>.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.unicode-codepoint-escape-syntax">
  <title>Unicode codepoint escape syntax</title>

  <para>
   This takes a Unicode codepoint in hexadecimal form, and outputs that
   codepoint in UTF-8 to a double-quoted string or a heredoc. Any valid
   codepoint is accepted, with leading 0's being optional.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
echo "\u{aa}";
echo "\u{0000aa}";
echo "\u{9999}";
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
ª
ª (same as before but with optional leading 0's)
香
]]>
   </screen>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.closure-call-method">
  <title><methodname>Closure::call</methodname></title>

  <para>
   <methodname>Closure::call</methodname> is a more performant, shorthand way
   of temporarily binding an object scope to a closure and invoking it.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
class A {private $x = 1;}

// Pre PHP 7 code
$getX = function() {return $this->x;};
$getXCB = $getX->bindTo(new A, 'A'); // intermediate closure
echo $getXCB();

// PHP 7+ code
$getX = function() {return $this->x;};
echo $getX->call(new A);
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
1
1
]]>
   </screen>
  </informalexample>
 </sect2>
 <sect2 xml:id="migration70.new-features.filtered-unserialize">
  <title>Filtered <function>unserialize</function></title>

  <para>
   This feature seeks to provide better security when unserializing objects on
   untrusted data. It prevents possible code injections by enabling the
   developer to whitelist classes that can be unserialized.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php

// converts all objects into __PHP_Incomplete_Class object
$data = unserialize($foo, ["allowed_classes" => false]);

// converts all objects into __PHP_Incomplete_Class object except those of MyClass and MyClass2
$data = unserialize($foo, ["allowed_classes" => ["MyClass", "MyClass2"]]);

// default behaviour (same as omitting the second argument) that accepts all classes
$data = unserialize($foo, ["allowed_classes" => true]);
]]>
   </programlisting>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.intlchar">
  <title><classname>IntlChar</classname></title>

  <para>
   The new <classname>IntlChar</classname> class seeks to expose additional
   ICU functionality. The class itself defines a number of static methods and
   constants that can be used to manipulate unicode characters.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php

printf('%x', IntlChar::CODEPOINT_MAX);
echo IntlChar::charName('@');
var_dump(IntlChar::ispunct('!'));
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
10ffff
COMMERCIAL AT
bool(true)
]]>
   </screen>
  </informalexample>

  <para>
   In order to use this class, the <link linkend="book.intl">Intl</link> extension must be installed.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.expectations">
  <title>Expectations</title>

  <para>
   Expectations are a
   backwards compatible enhancement to the older <function>assert</function>
   function. They allow for zero-cost assertions in production code, and
   provide the ability to throw custom exceptions when the assertion fails.
  </para>

  <para>
   While the old API continues to be maintained for compatibility,
   <function>assert</function> is now a language construct, allowing the first
   parameter to be an expression rather than just a <type>string</type> to be
   evaluated or a <type>bool</type> value to be tested.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
ini_set('assert.exception', 1);

class CustomError extends AssertionError {}

assert(false, new CustomError('Some error message'));
?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
Fatal error: Uncaught CustomError: Some error message
]]>
   </screen>
  </informalexample>

  <para>
   Full details on this feature, including how to configure it in both
   development and production environments, can be found on the manual page
   of the <function>assert</function> language construct.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.group-use-declarations">
  <title>Group <literal>use</literal> declarations</title>

  <para>
   Classes, functions and constants being imported from the same &namespace;
   can now be grouped together in a single &use.namespace; statement.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
// Pre PHP 7 code
use some\namespace\ClassA;
use some\namespace\ClassB;
use some\namespace\ClassC as C;

use function some\namespace\fn_a;
use function some\namespace\fn_b;
use function some\namespace\fn_c;

use const some\namespace\ConstA;
use const some\namespace\ConstB;
use const some\namespace\ConstC;

// PHP 7+ code
use some\namespace\{ClassA, ClassB, ClassC as C};
use function some\namespace\{fn_a, fn_b, fn_c};
use const some\namespace\{ConstA, ConstB, ConstC};
?>
]]>
   </programlisting>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.generator-return-expressions">
  <title>Generator Return Expressions</title>

  <para>
   This feature builds upon the generator functionality introduced into PHP 5.5.
   It enables for a <literal>return</literal> statement to be used within a
   generator to enable for a final expression to be returned (return by
   reference is not allowed). This value can be fetched using the new 
   <literal>Generator::getReturn()</literal> method, which may only be used
   once the generator has finished yielding values.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php

$gen = (function() {
    yield 1;
    yield 2;

    return 3;
})();

foreach ($gen as $val) {
    echo $val, PHP_EOL;
}

echo $gen->getReturn(), PHP_EOL;
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
1
2
3
]]>
   </screen>
  </informalexample>

  <para>
   Being able to explicitly return a final value from a generator is a handy
   ability to have. This is because it enables for a final value to be returned
   by a generator (from perhaps some form of coroutine computation) that can be
   specifically handled by the client code executing the generator. This is far
   simpler than forcing the client code to firstly check whether the final
   value has been yielded, and then if so, to handle that value specifically.
  </para>
 </sect2>
 <sect2 xml:id="migration70.new-features.generator-delegation">
  <title>Generator delegation</title>

  <para>
   Generators can now delegate to another generator,
   <classname>Traversable</classname> object or <type>array</type>
   automatically, without needing to write boilerplate in the outermost
   generator by using the &yield.from; construct.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
function gen()
{
    yield 1;
    yield 2;
    yield from gen2();
}

function gen2()
{
    yield 3;
    yield 4;
}

foreach (gen() as $val)
{
    echo $val, PHP_EOL;
}
?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
1
2
3
4
]]>
   </screen>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.intdiv">
  <title>Integer division with <function>intdiv</function></title>

  <para>
   The new <function>intdiv</function> function performs an integer division
   of its operands and returns it.
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
var_dump(intdiv(10, 3));
?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
int(3)
]]>
   </screen>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.session-options">
  <title>Session options</title>

  <para>
   <function>session_start</function> now accepts an <type>array</type> of
   options that override the
   <link linkend="session.configuration">session configuration directives</link>
   normally set in php.ini.
  </para>

  <para>
   These options have also been expanded to support
   <link linkend="ini.session.lazy-write">session.lazy_write</link>, which is
   on by default and causes PHP to only overwrite any session file if the
   session data has changed, and <literal>read_and_close</literal>, which is
   an option that can only be passed to <function>session_start</function> to
   indicate that the session data should be read and then the session should
   immediately be closed unchanged.
  </para>

  <para>
   For example, to set
   <link linkend="ini.session.cache-limiter">session.cache_limiter</link> to
   <literal>private</literal> and immediately close the session after reading
   it:
  </para>

  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
session_start([
    'cache_limiter' => 'private',
    'read_and_close' => true,
]);
?>
]]>
   </programlisting>
  </informalexample>
 </sect2>

 <sect2 xml:id="migration70.new-features.preg-repace-callback-array-function">
  <title><function>preg_replace_callback_array</function></title>

  <para>
   The new <function>preg_replace_callback_array</function> function enables
   code to be written more cleanly when using the
   <function>preg_replace_callback</function> function. Prior to PHP 7,
   callbacks that needed to be executed per regular expression required the
   callback function to be polluted with lots of branching.
  </para>

  <para>
   Now, callbacks can be registered to each regular expression using an
   associative array, where the key is a regular expression and the value is a
   callback.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.csprng-functions">
  <title>CSPRNG Functions</title>

  <para>
   Two new functions have been added to generate cryptographically secure
   integers and strings in a cross platform way:
   <function>random_bytes</function> and <function>random_int</function>.
  </para>
 </sect2>

 <sect2 xml:id="migration70.new-features.list-arrayaccess">
  <title>
   <function>list</function> can always unpack objects implementing
   <classname>ArrayAccess</classname>
  </title>

  <para>
   Previously, <function>list</function> was not guaranteed to operate
   correctly with objects implementing <classname>ArrayAccess</classname>.
   This has been fixed.
  </para>
 </sect2>
 
 <sect2 xml:id="migration70.new-features.others">
  <title>Other Features</title>
  <itemizedlist>
   <listitem>
    <simpara>
     Class member access on cloning has been added,
     e.g. <literal>(clone $foo)-&gt;bar()</literal>.
    </simpara>
   </listitem>
  </itemizedlist>
 </sect2>
</sect1>

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