PHP Judgment class existence function class_exists usage Analysis _php skill

In this paper, we analyze whether there is a function class_exists usage in PHP judgment class. Share to everyone for your reference. Specifically as follows:

If we want to judge whether a class can be used, we can use the Class_exists function to judge it, let's look at a few examples below.

BOOL Class_exists (String $class _name [, bool $autoload = True])
Whether this feature is given a class that is defined for checking. This function checks whether or not the given class has been defined.
Returns True if Class_name is a defined class, it returns FALSE.

Examples are as follows:

Copy Code code as follows:

function __autoload ($class)
{
Include ($class. '. php ');
Check to whether the include declared the class
if (!class_exists ($class, false)) {
Trigger_error ("Unable to load class: $class", e_user_warning);
}
}
if (class_exists (' MyClass ')) {
$myclass = new MyClass ();
}

I hope this article will help you with your PHP program design.