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<refentry xml:id="function.is-subclass-of" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>is_subclass_of</refname>
  <refpurpose>Checks if the object has this class as one of its parents or implements it</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>is_subclass_of</methodname>
   <methodparam><type>mixed</type><parameter>object</parameter></methodparam>
   <methodparam><type>string</type><parameter>class_name</parameter></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>allow_string</parameter><initializer>&true;</initializer></methodparam>
  </methodsynopsis>
  <para>
   Checks if the given <parameter>object</parameter> has the class
   <parameter>class_name</parameter> as one of its parents or implements it.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>object</parameter></term>
     <listitem>
      <para>
       A class name or an object instance. No error is generated if the class does not exist.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>class_name</parameter></term>
     <listitem>
      <para>
       The class 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</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>
   This function returns &true; if the object <parameter>object</parameter>,
   belongs to a class which is a subclass of
   <parameter>class_name</parameter>, &false; otherwise.
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>is_subclass_of</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// define a class
class WidgetFactory
{
  var $oink = 'moo';
}

// define a child class
class WidgetFactory_Child extends WidgetFactory
{
  var $oink = 'oink';
}

// create a new object
$WF = new WidgetFactory();
$WFC = new WidgetFactory_Child();

if (is_subclass_of($WFC, 'WidgetFactory')) {
  echo "yes, \$WFC is a subclass of WidgetFactory\n";
} else {
  echo "no, \$WFC is not a subclass of WidgetFactory\n";
}


if (is_subclass_of($WF, 'WidgetFactory')) {
  echo "yes, \$WF is a subclass of WidgetFactory\n";
} else {
  echo "no, \$WF is not a subclass of WidgetFactory\n";
}


// usable only since PHP 5.0.3
if (is_subclass_of('WidgetFactory_Child', 'WidgetFactory')) {
  echo "yes, WidgetFactory_Child is a subclass of WidgetFactory\n";
} else {
  echo "no, WidgetFactory_Child is not a subclass of WidgetFactory\n";
}
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
yes, $WFC is a subclass of WidgetFactory
no, $WF is not a subclass of WidgetFactory
yes, WidgetFactory_Child is a subclass of WidgetFactory
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><function>is_subclass_of</function> using interface example</title>
    <programlisting role="php">
<![CDATA[
<?php
// Define the Interface
interface MyInterface
{
  public function MyFunction();
}

// Define the class implementation of the interface
class MyClass implements MyInterface
{
  public function MyFunction()
  {
    return "MyClass Implements MyInterface!";
  }
}

// Instantiate the object
$my_object = new MyClass;

// Works since 5.3.7

// Test using the object instance of the class
if (is_subclass_of($my_object, 'MyInterface')) {
  echo "Yes, \$my_object is a subclass of MyInterface\n";
} else {
  echo "No, \$my_object is not a subclass of MyInterface\n";
}

// Test using a string of the class name
if (is_subclass_of('MyClass', 'MyInterface')) {
  echo "Yes, MyClass is a subclass of MyInterface\n";
} else {
  echo "No, MyClass is not a subclass of MyInterface\n";
}
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Yes, $my_object is a subclass of MyInterface
Yes, MyClass is a subclass of MyInterface
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  &note.uses-autoload;
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>get_class</function></member>
    <member><function>get_parent_class</function></member>
    <member><function>is_a</function></member>
    <member><function>class_parents</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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