instanceof
instanceof is used to determine whether a PHP variable is an instantiated object of a certain class. It is related to the function is_a().
instanceof has a higher precedence than ! operator, so it is applied before the latter. In case of confusion, use parenthesis.
instanceof does not check that the checked class exists: it just checks that the provided object match the class name. If a typo happens in the class name or the class does not exists, the operator fails every time.
<?php
if ($user instanceof Administrator) {
$user->admin();
}
// If The user is not of class User...
if ( !$user instanceof User ) {
//if ( !($user instanceof User) ) {
$user->admin();
}
var_dump($user instanceof UndefinedClass); // false
?>