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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<refentry xml:id="function.class-exists" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>class_exists</refname>
<refpurpose>Checks if the class has been defined</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<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><initializer>true</initializer></methodparam>
</methodsynopsis>
<para>
This function checks whether or not the given class has been defined.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>class_name</parameter></term>
<listitem>
<para>
The class name. The name is matched in a case-insensitive manner.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>autoload</parameter></term>
<listitem>
<para>
Whether or not to call &link.autoload; by default.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns &true; if <parameter>class_name</parameter> is a defined class,
&false; otherwise.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>5.0.2</entry>
<entry>
No longer returns &true; for defined interfaces. Use
<function>interface_exists</function>.
</entry>
</row>
<row>
<entry>5.0.0</entry>
<entry>
The <parameter>autoload</parameter> parameter was added.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>class_exists</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// Check that the class exists before trying to use it
if (class_exists('MyClass')) {
$myclass = new MyClass();
}
?>
]]>
</programlisting>
</example>
<example>
<title><parameter>autoload</parameter> parameter example</title>
<programlisting role="php">
<![CDATA[
<?php
function __autoload($class)
{
include($class . '.php');
// Check to see whether the include declared the class
if (!class_exists($class, false)) {
trigger_error("Unable to load class: $class", E_USER_WARNING);
}
}
if (class_exists('MyClass')) {
$myclass = new MyClass();
}
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>function_exists</function></member>
<member><function>interface_exists</function></member>
<member><function>get_declared_classes</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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