PHP: Hypertext Preprocessor (original) (raw)
class_exists
(PHP 4, PHP 5, PHP 7, PHP 8)
class_exists — Checks if the class has been defined
Description
Parameters
class
The class name. The name is matched in a case-insensitive manner.
autoload
Whether to autoload if not already loaded.
Return Values
Returns [true](reserved.constants.php#constant.true) if class is a defined class,[false](reserved.constants.php#constant.false) otherwise.
Examples
Example #1 class_exists() example
<?php // Check that the class exists before trying to use it if (class_exists('MyClass')) { $myclass = new MyClass(); }?>
Example #2 autoload parameter example
`<?php
spl_autoload_register(function ($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
Found A Problem?
giunta dot gaetano at gmail dot com ¶
11 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
`
4 years ago
`Note: class_exists() check only classes!
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 $autoload Whether to call spl_autoload()
- @return bool
*/
function structure_exists(string name,boolname, bool name,boolautoload = true): bool
{
return class_exists($name, $autoload)
|| interface_exists($name, $autoload)
|| trait_exists($name, $autoload);
}
?>`
rn at alpha9marketing dot com ¶
11 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.
`
15 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.
`
11 years ago
`Hi guys!
Be careful and don't forget about second boolean argument $autoload (TRUE by default) when check exists class after spl_autoload_register. Propose short example
file second.php
file index.php
<?php
class First
{
function first($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', $bool = false); //Not exist!
?>
Because __autoload executing much earlier than boolean returned, imho..`
10 months ago
`` Beware that \class_exists() returns true for enums.
Having this in mind, the correct check for a class existence is:
``
richard at richard-sumilang dot com ¶
17 years ago
`[ >= PHP 5.3]
If you are checking if a class exists that is in a specific namespace then you have to pass in the full path to the class:
echo (class_exists("com::richardsumilang::common::MyClass")) ? "Yes" : "No";
`
anonymous at somewhere dot tld ¶
21 years ago
`If you have a directory of classes you want to create. (Modules in my instance)... you can do it like that
MODULE_PATH) && dh=opendir(dh = opendir(dh=opendir(this->MODULE_PATH)) { while (($file = readdir($dh)) !== false) { if (preg_match("/(Mod[a-zA-Z0-9]+).php/", file,file, file,matches)>0) { // include and create the class require_once($this->MODULE_PATH."/".$file); modules[]=newmodules[] = new modules[]=newmatches[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
`
13 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.
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=newvar = new var=newclassname(); } 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.
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!
`