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is_subclass_of — Finds out whether an object's class is a subclass of a given class.


bool is_subclass_of(obj, parent_class_name);
object obj: Object to test for being a subclass of parent_class_name
string parent_class_name: Name of the class to test with


TRUE if the given object is a subclass of the given class; FALSE for all other cases


is_subclass_of() is used to determine whether the class from which a given object is instantiated is a subclass of the given class.


PHP Version: 4.0b4+


Example 108. Determine whether a class is a subclass of another class

class vehicle {
    var $passenger_num;
    var $power_source;
    var $travel_medium;

class jinrikisha extends vehicle {
    var $wheels = 2;

    function jinrikisha () {
        $this->passenger_num = '1 to 2';
        $this->power_source = 'human/pulled';
        $this->travel_medium = 'land/roads';

$my_jinrikisha = new jinrikisha ();
$class = get_class ($my_jinrikisha);
$parent_class = 'vehicle';

print "Object \$my_jinrikisha is an instance of class <i>$class</i>.\n";

$qualifier = is_subclass_of ($my_jinrikisha, $parent_class) ? 'is' : 'is not';

print "Class <i>$class</i> $qualifier a subclass of class <i>$parent_class</i>.";

PHP Functions Essential Reference. Copyright © 2002 by New Riders Publishing (Authors: Zak Greant, Graeme Merrall, Torben Wilson, Brett Michlitsch). This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at The authors of this book have elected not to choose any options under the OPL. This online book was obtained from and is designed to provide information about the PHP programming language, focusing on PHP version 4.0.4 for the most part. The information is provided on an as-is basis, and no warranty or fitness is implied. All persons and entities shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained in this book.

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