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class_exists — Tests whether a class is defined.


bool class_exists(class_name);
string class_name: Name of the class whose existence is being tested


TRUE if the class exists; FALSE for all other cases


class_exists() is used to check whether a class has been defined. If the class has been defined, the function returns TRUE; otherwise, it returns FALSE.


PHP Version: 4.0b4+

See also

To find the type of a variable:


To find out whether a variable is an object:



Example 101. Check to see whether a class is defined

// Why no class can be a nihilist
class nihilist {
    function nihilist () {
        print "";   // Ha ha - sorry for the crummy nihilist humor...

if (class_exists ('nihilist'))
    print "Class <i>nihilist</i> exists.";

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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