anonymous.xml

<?xml version="1.0" encoding="utf-8"?>
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<sect1 xml:id="language.oop5.anonymous" xmlns="http://docbook.org/ns/docbook">
 <title>Anonymous classes</title>

 <para>
  Anonymous classes are useful when simple, one-off objects need to be created.
 </para>

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

// Using an explicit class
class Logger
{
    public function log($msg)
    {
        echo $msg;
    }
}

$util->setLogger(new Logger());

// Using an anonymous class
$util->setLogger(new class {
    public function log($msg)
    {
        echo $msg;
    }
});
]]>
  </programlisting>
 </informalexample>

 <para>
  They can pass arguments through to their constructors, extend other classes,
  implement interfaces, and use traits just like a normal class can:
 </para>

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

class SomeClass {}
interface SomeInterface {}
trait SomeTrait {}

var_dump(new class(10) extends SomeClass implements SomeInterface {
    private $num;

    public function __construct($num)
    {
        $this->num = $num;
    }

    use SomeTrait;
});
]]>
  </programlisting>
  &example.outputs;
  <screen>
<![CDATA[
object(class@anonymous)#1 (1) {
  ["Command line code0x104c5b612":"class@anonymous":private]=>
  int(10)
}
]]>
  </screen>
 </informalexample>

 <para>
  Nesting an anonymous class within another class does not give it access to
  any private or protected methods or properties of that outer class. In order
  to use the outer class' protected properties or methods, the anonymous class
  can extend the outer class. To use the private properties of
  the outer class in the anonymous class, they must be passed through its
  constructor:
 </para>

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

class Outer
{
    private $prop = 1;
    protected $prop2 = 2;

    protected function func1()
    {
        return 3;
    }

    public function func2()
    {
        return new class($this->prop) extends Outer {
            private $prop3;

            public function __construct($prop)
            {
                $this->prop3 = $prop;
            }

            public function func3()
            {
                return $this->prop2 + $this->prop3 + $this->func1();
            }
        };
    }
}

echo (new Outer)->func2()->func3();
]]>
  </programlisting>
  &example.outputs;
  <screen>
<![CDATA[
6
]]>
  </screen>
 </informalexample>

 <para>
  All objects created by the same anonymous class declaration are instances of
  that very class.
 </para>

 <informalexample>
  <programlisting role="php">
<![CDATA[
<?php
function anonymous_class()
{
    return new class {};
}

if (get_class(anonymous_class()) === get_class(anonymous_class())) {
    echo 'same class';
} else {
    echo 'different class';
}]]>
 </programlisting>
 &example.outputs;
 <screen>
<![CDATA[
same class
]]>
  </screen>
 </informalexample>

 <note>
  <para>
   Note that anonymous classes are assigned a name by the engine, as
   demonstrated in the following example. This name has to be regarded an
   implementation detail, which should not be relied upon.
  </para>
  <informalexample>
   <programlisting role="php">
<![CDATA[
<?php
echo get_class(new class {});
]]>
  </programlisting>
  &example.outputs.similar;
  <screen>
<![CDATA[
class@anonymous/in/oNi1A0x7f8636ad2021
]]>
   </screen>
  </informalexample>
 </note>

 <sect2 xml:id="language.oop5.anonymous.readonly">
  <title>Readonly anonymous classes</title>
  <simpara>
   As of PHP 8.3.0, the <literal>readonly</literal> modifier can
   be applied to anonymous classes.
  </simpara>
  <example xml:id="language.oop5.anonymous.readonly.example">
   <title>Defining a readonly anonymous class</title>
   <programlisting role="php">
    <![CDATA[
<?php
// Using an anonymous class
var_dump(new readonly class('[DEBUG]') {
    public function __construct(private string $prefix)
    {
    }

    public function log($msg)
    {
        echo $this->prefix . ' ' . $msg;
    }
});
]]>
   </programlisting>
  </example>
 </sect2>
</sect1>
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