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Last updated: Fri, 26 Jan 2007

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# class_exists

(PHP 4, PHP 5)

class_exists -- Проверяет был ли объявлен класс

## Описание

bool class_exists ( string class_name )

Функция возвращает `TRUE` если класс`class_name` был объявлен. В противном случае функция возвращает `FALSE`.

См. также get_declared_classes().

add a note User Contributed Notes
class_exists
Frayja
01-Jun-2006 01:42
`Like someone else pointed out class_exists() is case-INsensitive.
Using in_array() which is case-sensitive, the following function is a case-sensitive version of class_exists().
<?php
function class_exists_sensitive( $classname )
{
return ( class_exists( $classname ) && in_array( $classname, get_declared_classes() ) );
}
?>`
josh at digitalfruition dot com
25-Jun-2005 11:23
`Just to note, class names appear to be case INsensitive. (At least at the time of writing in PHP 4.3.9). Take the following example:
<?php
class Foo { var $myVar; }
class Foo_Bar extends Foo { var $myVar2;}
echo class_exists('Foo'); //true
echo class_exists('foo'); //true
echo class_exists('Foo_Bar'); // true
echo get_class_parent('Foo_Bar'); // foo (NOTE: NOT Foo!)
?>`
andrey at php dot net
24-Oct-2004 04:43
`In 5.0.0 and 5.0.1 there was no interface_exists() and in these versions class_exists() used to return TRUE for known interfaces. Starting 5.0.2 this is no more.`
06-Apr-2004 05:04
`Just a note that at least PHP 4.3.1 seems to crash under some situations if you call class_exists($foo) where $foo is an array (that is, the calling code is incorrect but the error recovery is far from perfect).`
anonymous at somewhere dot tld
17-Jul-2003 12:20
`If you have a directory of classes you want to create. (Modules in my instance)... you can do it like that
<?php
if (is_dir($this->MODULE_PATH) && $dh = opendir($this->MODULE_PATH)) {
while (($file = readdir($dh)) !== false) {
if (preg_match("/(Mod[a-zA-Z0-9]+).php/", $file, $matches)>0) {
// include and create the class
require_once($this->MODULE_PATH."/".$file);
$modules[] = new $matches[1]();
}
}
} else {
exit;
}
?>
//---
Here the rule is that all modules are on the form
ModModulename.php and that the class has the same name as the file.
The $modules array has all the classes initialized after this code`
cristiano at aspatech dot com dot br
24-Jun-2002 11:36
`This can be veeeery usefull if you use classes that uses other classes, which can be used in your front end. In other words, when you lost the control of which classes are declared in which point of the application, that can generate the "Cannot redeclare class". Use like
<?php
if ( !class_exists( "YourClass" ) ) {
class YourClass {
//your code
}
}
?>
Thats it... Resolve all your problems =)`
spamless_blair at nb dot net
09-Oct-2001 01:48
`I have a script that includes various class libraries depending on what is contained in the constant _INCLUDE_LIST which is a comma-delimited string.
define('_INCLUDE_LIST', 'CORE, LIB_DATA, LIB_EMAIL');
I use class_exists() to determine if a class definition has been included before creating an instance of it.
if(class_exists('CMySQLConnection')) $oData = new CMySQLConnection;
Hope it is helpful for someone!
-Jason Garber
IonZoft.com`
emurano at optushome dot com dot au
09-Mar-2001 12:35
`Multiple inclusion protection can be achieved in php3 and for non class related code, for example:
<?php
if(!defined("_SOME_UNIQUE_CONSTANT_")) {
define("_SOME_UNIQUE_CONSTANT_",TRUE);
// Your protected code here
}
?>
Make sure that you use a different constant for each protected piece of code. Generally this is used on a file per file basis. Just #ifndef in C!`
add a note
get_class_methods call_user_method

Last updated: Fri, 26 Jan 2007
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