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class_exists

(PHP 4, PHP 5, PHP 7, PHP 8)

class_existsVerifica si la clase ha sido definida

Descripción

class_exists(string $class_name, bool $autoload = true): bool

Esta función verifica si la clase dada ha sido definida o no.

Parámetros

class_name

El nombre de la clase. El nombre es coincidido de manera insensible a mayúsculas y minúsculas.

autoload

Indica si ha de llamarse __autoload o no de forma predeterminada.

Valores devueltos

Devuelve true si class_name es una clase definida, false de lo contrario.

Historial de cambios

Versión Descripción
5.0.2 Ya no devuelve true para interfaces definidas. En ese caso se debe usar interface_exists().

Ejemplos

Ejemplo #1 Ejemplo de class_exists()

<?php
// Verificar que la clase exista antes de usarla
if (class_exists('MiClase')) {
$mi_clase = new MiClase();
}

?>

Ejemplo #2 Ejemplo del parámetro autoload

<?php
function __autoload($clase)
{
include(
$clase . '.php');

// Verificar si la sentencia include declaró la clase
if (!class_exists($clase, false)) {
trigger_error("No es posible cargar la clase: $clase", E_USER_WARNING);
}
}

if (
class_exists('MiClase')) {
$mi_clase = new MiClase();
}

?>

Ver también

add a note

User Contributed Notes 9 notes

up
50
giunta dot gaetano at gmail dot com
10 years ago
If you are using aliasing to import namespaced classes, take care that class_exists will not work using the short, aliased class name - apparently whenever a class name is used as string, only the full-namespace version can be used

use a\namespaced\classname as coolclass;

class_exists( 'coolclass' ) => false
up
10
info at ensostudio dot ru
3 years ago
Note: class_exists() check only classes!
<?php
interface DemoInterface {};
var_dump(class_exists('DemoInterface')); // false
trait DemoTrait {};
var_dump(class_exists('DemoTrait')); // false
class DemoClass {};
var_dump(class_exists('DemoClass')); // true
?>

Common function:
<?php
/**
* Checks if the class/trait/interface has been defined.
*
* @param string $name The case-insensitive name of class/trait/interface
* @param bool $autoload Whether to call spl_autoload()
* @return bool
*/
function structure_exists(string $name, bool $autoload = true): bool
{
return
class_exists($name, $autoload)
||
interface_exists($name, $autoload)
||
trait_exists($name, $autoload);
}
?>
up
15
rn at alpha9marketing dot com
10 years ago
Beware: class_exists is case-INsensitive, as is class instantiation.

php > var_dump(class_exists("DomNode"));
bool(true)
php > var_dump(class_exists("DOMNode"));
bool(true)
php > var_dump(class_exists("DOMNodE"));
bool(true)
php > $x = new DOMNOdE();
php > var_dump(get_class($x));
string(7) "DOMNode"

(tested with PHP 5.5.10 on Linux)

This can cause some headaches in correlating class names to file names, especially on a case-sensitive file system.
up
13
Klaus
14 years ago
If you recursively load several classes inside an autoload function (or mix manual loading and autoloading), be aware that class_exists() (as well as get_declared_classes()) does not know about classes previously loaded during the *current* autoload invocation.

Apparently, the internal list of declared classes is only updated after the autoload function is completed.
up
12
spam at wikicms dot org
10 years ago
Hi guys!
Be careful and don't forget about second boolean argument $autoload (TRUE by default) when check exists class after spl_autoload_register. Propose short example
file second.php
<?php
class Second {}
?>
file index.php
<?php
class First
{
function
first($class, $bool) {
spl_autoload_register( function($class) {
require
strtolower($class) . '.php';
});
echo
class_exists($class, $bool)?'Exist!!!!':'Not exist!';
}
}

new
First($class = 'Second', $bool = true); //Exist!!!!
new First($class = 'Second', $bool = false); //Not exist!
?>
Because __autoload executing much earlier than boolean returned, imho..
up
10
richard at richard-sumilang dot com
16 years ago
[ >= 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";
up
2
anonymous at somewhere dot tld
20 years ago
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
up
0
toocoolone at gmail dot com
12 years ago
I'm running PHP 5.3.4 on Windows 7 and had some difficulty autoloading classes using class_exists(). In my case, when I checked for the class and it didn't exist, class_exists automatically threw a system Exception. I was also throwing my own exception resulting in an uncaught exception.

<?php
/**
* Set my include path here
*/
$include_path = array( '/include/this/dir', '/include/this/one/too' );
set_include_path( $include_path );
spl_autoload_register();
/**
* Assuming I have my own custom exception handler (MyException) let's
* try to see if a file exists.
*/
try {
if( !
file_exists( 'myfile.php' ) ) {
throw new
MyException('Doh!');
}
include(
'myfile.php' );
}
catch(
MyException $e ) {
echo
$e->getMessage();
}
/**
* The above code either includes myfile.php or throws the new MyException
* as expected. No problem right? The same should be true of class_exists(),
* right? So then...
*/
$classname = 'NonExistentClass';
try {
if( !
class_exists( $classname ) ) {
throw new
MyException('Double Doh!');
}
$var = new $classname();
}
catch(
MyException $e ) {
echo
$e->getMessage();
}
/**
* Should throw a new instance of MyException. But instead I get an
* uncaught LogicException blah blah blah for the default Exception
* class AND MyException. I only catch MyException so we've got on
* uncaught resulting in the dreaded LogicException error.
*/
?>

By registering an additional autoload handler function that did nothing, I was able to stop throwing the extra Exception and only throw my own.

<?php
/**
* Set my include path here
*/
$include_path = array( '/include/this/dir', '/include/this/one/too' );
set_include_path( $include_path );
spl_autoload_register();
spl_autoload_register( 'myAutoLoad' ); // Add these two and no worries...
function myAutoLoad() {}
/**
* By registering the additional custom autoload function that does nothing
* class_exists() returns only boolean and does NOT throw an uncaught Exception
*/
?>

Found this buried in some search results. I don't remember the page URL but if it would have been here it might have saved me some time!
up
-13
azrael dot com at gmail dot com
15 years ago
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());
?>
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