class_alias
If spl_autoload_register() had been called, then function will try autoload class if it does not exists.
Use instead
<?php
in_array($class_name, get_declared_classes());
?>
class_exists
(PHP 4, PHP 5)
class_exists — Checks if the class has been defined
Beschreibung
bool class_exists
( string $class_name
[, bool $autoload = true
] )
Diese Funktion prüft ob eine bestimmte Klasse definiert wurde.
Parameter-Liste
- class_name
-
Der Klassenname. Groß- und Kleinschreibung wird bein Vergleich nicht beachtet.
- autoload
-
Gibt an ob __autoload genutzt werden soll. Vorgabewert ist TRUE.
Rückgabewerte
Gibt TRUE zurück falls die Klasse class_name definiert ist, sonst FALSE.
Changelog
| Version | Beschreibung |
|---|---|
| 5.0.2 | Die Funktion liefert nun nicht mehr TRUE für Interfaces. Nutzen Sie hierfür interface_exists(). |
| 5.0.0 | Der autoload Parameter wurde hinzugefügt. |
Beispiele
Beispiel #1 class_exists() Beispiel
<?php
// prüft vor Benutzung ob die gewünschte Klasse definiert ist
if (class_exists('MyClass')) {
$myclass = new MyClass();
}
?>
Beispiel #2 autoload Parameter Beispiel
<?php
function __autoload($class)
{
include($class . '.php');
// Prüft ob die includierte Datei die Klasse tatsächlich definiert
if (!class_exists($class, false)) {
trigger_error("Die Klasse $class kann nicht geladen werden", E_USER_WARNING);
}
}
if (class_exists('MyClass')) {
$myclass = new MyClass();
}
?>
Siehe auch
- function_exists() - Falls die angegebene Funktion definiert ist, wird TRUE zurück gegeben
- interface_exists() - Checks if the interface has been defined
- get_declared_classes() - Ermittelt die Namen der definierten Klassen
add a note
User Contributed Notesclass_exists
azrael dot com at gmail dot com
12-Dec-2008 12:14
12-Dec-2008 12:14
Anonymous
29-Nov-2008 06:27
29-Nov-2008 06:27
If you planned to use utf-8 in classes or variables names, remember that locale has to be properly set firstly, e.g.
<?php
locale (LC_ALL, 'ru_RU.UTF-8');
?>
or it turn into errors.
Radek @ cz
06-May-2008 01:43
06-May-2008 01:43
If you want to combat many class includes effectively, define your own autoloader function and spl_autoload_register() that autoloader.
richard at richard-sumilang dot com
27-Mar-2008 08:56
27-Mar-2008 08:56
[ >= PHP 5.3]
If you are checking if a class exists that is in a specific namespace then you have to pass in the full path to the class:
echo (class_exists("com::richardsumilang::common::MyClass")) ? "Yes" : "No";
Frayja
01-Jun-2006 08:42
01-Jun-2006 08:42
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( $classname, get_declared_classes() ) );
}
?>
06-Apr-2004 12:04
Just a note that at least PHP 4.3.1 seems to crash under some situations if you call class_exists($foo) where $foo is an array (that is, the calling code is incorrect but the error recovery is far from perfect).
anonymous at somewhere dot tld
17-Jul-2003 07:20
17-Jul-2003 07:20
If you have a directory of classes you want to create. (Modules in my instance)... you can do it like that
<?php
if (is_dir($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