is_subclass_of

(PHP 4, PHP 5)

is_subclass_of — Checks if the object has this class as one of its parents

Description

bool is_subclass_of ( mixed $object , string $class_name )

Checks if the given object has the class class_name as one of its parents.

Parameters

object: A class name or an object instance
class_name: The class name

Return Values

This function returns TRUE if the object object , belongs to a class which is a subclass of class_name , FALSE otherwise.

Changelog

Version	Description
5.0.3	You may also specify the `object` parameter as a string (the name of the class)

Examples

Example #1 is_subclass_of() example


<?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";
}
?>

The above example will output:

yes, $WFC is a subclass of WidgetFactory
no, $WF is not a subclass of WidgetFactory
yes, WidgetFactory_Child is a subclass of WidgetFactory


It would appear that is_subclass_of is case insensitive unlike get_class in php5.


i.e.





<?php


class fooBar {}


class bar extends fooBar {}





assert(get_class(new fooBar()) == "fooBar");


assert(is_subclass_of(new bar(), "foobar") == true);


?>





i run across this while migrating some code from php4 to php5 and the code would only half-the-time break.

Ondra Zizka
13-Oct-2006 07:31


For PHP4:



/** Returns whether specified class is subclass of the other class. */

function is_subclass($sClass, $sExpectedParentClass){

    do if( $sExpectedParentClass === $sClass ) return true;

    while( false != ($sClass = get_parent_class($sClass)) );

    return false;

}

// Test:

class A {} class B extends A {} class C extends B {} echo (int) is_subclass('C', 'A');

gunniboyh at web dot de
20-May-2006 08:16


is_subclass_of() works also with classes between the class of obj and the superclass.



example:

<?php

class A {};

class B extends A {};

class C extends B {};



$foo=new C();

echo ((is_subclass_of($foo,'A')) ? 'true' : 'false');

?>



echoes 'true' .

01-Oct-2005 08:32


this function does not check interfaces, unlike instanceof operator.

youcantryreachingme at REMOVEME dot hotmail dot com
21-Mar-2005 08:15


A bug report at http://pear.php.net/bugs/bug.php?id=2975 indicates that the "is_subclass_of" function can return the error message:



Warning: Unknown class passed as parameter



in the event that the class represented by the second argument hasn't yet been instantiated.

add a note

method_exists

is_a

Last updated: Fri, 02 Jan 2009