call_user_method
If you want to combat many class includes effectively, define your own autoloader function and spl_autoload_register() that autoloader.
class_exists
(PHP 4, PHP 5)
class_exists — Verifica se una classe è stata definita
Descrizione
bool class_exists
( string $nome_classe
[, bool $autoload
] )
Questa funzione restituisce TRUE se la classe indicata dal parametro nome_classe è stata definita, altrimenti restituisce FALSE .
Example #1 Esempio di uso di class_exists()
<?php
// Verifica se la classe esiste prima di richiamarla
if (class_exists('MyClass')) {
$myclass = new MyClass();
}
?>
class_exists(), per default, tenta di eseguire __autoload, se non si desidera che class_exists() esegua __autoload(), impostare il parametro autoload a FALSE.
Example #2 Esempio di uso di autoload
<?php
function __autoload($class)
{
include($class . '.php');
// Check to see it the include defined the class
if ( !class_exists($class, false) ) {
trigger_error("Unable to load class $class", E_USER_ERROR);
}
}
if( class_exists('MyClass') ) {
$myclass = new MyClass();
}
?>
Nota: Il parametro autoload è stato aggiunto in PHP 5
Vedere anche interface_exists() e get_declared_classes().
add a note
User Contributed Notesclass_exists
Radek @ cz
06-May-2008 03:43
06-May-2008 03:43
richard at richard-sumilang dot com
27-Mar-2008 09:56
27-Mar-2008 09:56
[ >= 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 10:42
01-Jun-2006 10:42
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( $classname, get_declared_classes() ) );
}
?>
06-Apr-2004 02:04
Just a note that at least PHP 4.3.1 seems to crash under some situations if you call class_exists($foo) where $foo is an array (that is, the calling code is incorrect but the error recovery is far from perfect).
anonymous at somewhere dot tld
17-Jul-2003 09:20
17-Jul-2003 09:20
If you have a directory of classes you want to create. (Modules in my instance)... you can do it like that
<?php
if (is_dir($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