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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.is-a" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>is_a</refname>
<refpurpose>Checks whether the object is of a given type or subtype</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>bool</type><methodname>is_a</methodname>
<methodparam><type>mixed</type><parameter>object_or_class</parameter></methodparam>
<methodparam><type>string</type><parameter>class</parameter></methodparam>
<methodparam choice="opt"><type>bool</type><parameter>allow_string</parameter><initializer>&false;</initializer></methodparam>
</methodsynopsis>
<para>
Determines if the given <parameter>object_or_class</parameter> is the
<parameter>class</parameter> object type,
or has <parameter>class</parameter> as one of its supertypes.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>object_or_class</parameter></term>
<listitem>
<para>
A class name or an object instance.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>class</parameter></term>
<listitem>
<para>
The class or interface name
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>allow_string</parameter></term>
<listitem>
<para>
If this parameter set to &false;, string class name as <parameter>object_or_class</parameter>
is not allowed. This also prevents from calling autoloader if the class doesn't exist.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns &true; if <parameter>object_or_class</parameter> is the
<parameter>class</parameter> object type,
or has <parameter>class</parameter> as one of its supertypes, &false; otherwise.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>is_a</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// define a class
class WidgetFactory
{
var $oink = 'moo';
}
// create a new object
$WF = new WidgetFactory();
if (is_a($WF, 'WidgetFactory')) {
echo "yes, \$WF is still a WidgetFactory\n";
}
?>
]]>
</programlisting>
</example>
<example>
<title>Using the <emphasis>instanceof</emphasis> operator</title>
<programlisting role="php">
<![CDATA[
<?php
if ($WF instanceof WidgetFactory) {
echo 'Yes, $WF is a WidgetFactory';
}
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>get_class</function></member>
<member><function>get_parent_class</function></member>
<member><function>is_subclass_of</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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