doc-en/reference/classobj/functions/class-alias.xml

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<refentry xml:id="function.class-alias" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>class_alias</refname>
  <refpurpose>Creates an alias for a class</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>class_alias</methodname>
   <methodparam><type>string</type><parameter>class</parameter></methodparam>
   <methodparam><type>string</type><parameter>alias</parameter></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>autoload</parameter><initializer>&true;</initializer></methodparam>
  </methodsynopsis>
  <para>
   Creates an alias named <parameter>alias</parameter>
   based on the user defined class <parameter>class</parameter>.
   The aliased class is exactly the same as the original class.
  </para>
   <note>
   <simpara>
    As of PHP 8.3.0, <function>class_alias</function> also supports
    creating an alias of a PHP internal class.
   </simpara>
  </note>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>class</parameter></term>
     <listitem>
      <para>
       The original class.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>alias</parameter></term>
     <listitem>
      <para>
       The alias name for the class.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>autoload</parameter></term>
     <listitem>
      <para>
       Whether to <link linkend="language.oop5.autoload">autoload</link>
       if the original class is not found.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.3.0</entry>
      <entry>
       <function>class_alias</function> now supports creating an alias of an internal class.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>class_alias</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php

class Foo { }

class_alias('Foo', 'Bar');

$a = new Foo;
$b = new Bar;

// the objects are the same
var_dump($a == $b, $a === $b);
var_dump($a instanceof $b);

// the classes are the same
var_dump($a instanceof Foo);
var_dump($a instanceof Bar);

var_dump($b instanceof Foo);
var_dump($b instanceof Bar);

?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
bool(true)
bool(false)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    Class names are case-insensitive in PHP, and this is reflected in this
    function. Aliases created by <function>class_alias</function> are declared
    in lowercase. This means that for a class
    <literal>MyClass</literal>, the <code>class_alias('MyClass', 'MyClassAlias')</code>
    call will declare a new class alias named <literal>myclassalias</literal>.
   </para>
  </note>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>get_parent_class</function></member>
    <member><function>is_subclass_of</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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