<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.6 $ -->
<!-- splitted from ./en/functions/classobj.xml, last change in rev 1.11 -->
  <refentry id="function.class-exists">
   <refnamediv>
    <refname>class_exists</refname>
    <refpurpose>Checks if the class has been defined</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <methodsynopsis>
     <type>bool</type><methodname>class_exists</methodname>
     <methodparam><type>string</type><parameter>class_name</parameter></methodparam>
     <methodparam choice="opt"><type>bool</type><parameter>autoload</parameter></methodparam>
    </methodsynopsis>
    <para>
     This function returns &true; if the class given by
     <parameter>class_name</parameter> has been defined,
     &false; otherwise.
    </para>
    <para>
     <example>
      <title><function>class_exists</function> example</title>
      <programlisting role="php">
<![CDATA[
<?php
// Check the class exists before trying to use it
if (class_exists('MyClass')) {
    $myclass = new MyClass();
}

?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     <function>class_exists</function> will attempt to call &link.autoload; by
     default, if you don't want <function>class_exists</function> to 
     call &link.autoload;, you can set the parameter <parameter>autoload</parameter>
     to &false;.
    </para>
    <para>
     <example>
      <title><parameter>autoload</parameter> parameter example</title>
      <programlisting role="php">
<![CDATA[
<?php
function __autoload($class)
{
    include($class . '.php');

    // Check to see if the include declared the class
    if (!class_exists($class, false)) {
        trigger_error("Unable to load class: $class", E_USER_WARNING);
    }
}
    
if (class_exists('MyClass')) {
    $myclass = new MyClass();
}

?>
]]>
      </programlisting>
     </example>
    </para>
    <note>
     <para>
      The <parameter>autoload</parameter> parameter was added in PHP 5
     </para>
    </note>
    <simpara>
     See also <function>interface_exists</function>, and
     <function>get_declared_classes</function>.
    </simpara>
   </refsect1>
  </refentry>

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