class_exists
Cette fonction vérifie si une classe donnée a été définie.
Liste de paramètres
Le nom de la classe. Il est recherché de manière insensible à la casse.
Si l’on doit appeler autoload par défaut.
Valeurs de retour
Retourne true si class est une classe définie, false sinon.
Exemples
Exemple #1 Exemple avec class_exists()
// Vérifie que la classe existe avant de l’utiliser
if ( class_exists ( ‘MyClass’ )) $myclass = new MyClass ();
>
Exemple #2 Exemple avec le paramètre autoload
spl_autoload_register (function ( $class_name ) include $class_name . ‘.php’
// Vérifie si l’include a déclaré la classe
if (! class_exists ( $class_name , false )) throw new LogicException ( «Unable to load class: $class_name » );
>
>);
if ( class_exists ( MyClass ::class)) $myclass = new MyClass ();
>
Voir aussi
- function_exists() — Indique si une fonction est définie
- enum_exists() — Vérifie si l’énumération est définie
- interface_exists() — Vérifie si une interface a été définie
- get_declared_classes() — Liste toutes les classes définies dans PHP
User Contributed Notes 9 notes
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
Note: class_exists() check only classes!
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:
/**
* 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 );
>
?>
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.
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.
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
class Second <>
?>
file index.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..
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»;
If you have a directory of classes you want to create. (Modules in my instance). you can do it like that
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.
/**
* 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.
/**
* 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!
If spl_autoload_register() had been called, then function will try autoload class if it does not exists.
Use instead
in_array ( $class_name , get_declared_classes ());
?>
- Fonctions Classes/Objets
- class_alias
- class_exists
- enum_exists
- get_called_class
- get_class_methods
- get_class_vars
- get_class
- get_declared_classes
- get_declared_interfaces
- get_declared_traits
- get_mangled_object_vars
- get_object_vars
- get_parent_class
- interface_exists
- is_a
- is_subclass_of
- method_exists
- property_exists
- trait_exists
- __autoload
class_exists
This function checks whether or not the given class has been defined.
Parameters
The class name. The name is matched in a case-insensitive manner.
Whether to autoload if not already loaded.
Return Values
Returns true if class is a defined class, false otherwise.
Examples
Example #1 class_exists() example
// Check that the class exists before trying to use it
if ( class_exists ( ‘MyClass’ )) $myclass = new MyClass ();
>Example #2 autoload parameter example
spl_autoload_register (function ( $class_name ) include $class_name . ‘.php’ ;
// Check to see whether the include declared the class
if (! class_exists ( $class_name , false )) throw new LogicException ( «Unable to load class: $class_name » );
>
>);if ( class_exists ( MyClass ::class)) $myclass = new MyClass ();
>See Also
- function_exists() — Return true if the given function has been defined
- enum_exists() — Checks if the enum has been defined
- interface_exists() — Checks if the interface has been defined
- get_declared_classes() — Returns an array with the name of the defined classes
User Contributed Notes 9 notes
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
Note: class_exists() check only classes!
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:
/**
* 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 );
>
?>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.
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.
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
class Second <>
?>
file index.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..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»;
If you have a directory of classes you want to create. (Modules in my instance). you can do it like that
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.
/**
* 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.
/**
* 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!
If spl_autoload_register() had been called, then function will try autoload class if it does not exists.
Use instead
in_array ( $class_name , get_declared_classes ());
?>- Classes/Object Functions
- class_alias
- class_exists
- enum_exists
- get_called_class
- get_class_methods
- get_class_vars
- get_class
- get_declared_classes
- get_declared_interfaces
- get_declared_traits
- get_mangled_object_vars
- get_object_vars
- get_parent_class
- interface_exists
- is_a
- is_subclass_of
- method_exists
- property_exists
- trait_exists
- __autoload