instanceof
Type Operators
instanceof is used to determine whether a PHP variable is an instantiated object of a certain class:
Example #1 Using instanceof with classes
<?php class MyClass { } class NotMyClass { } $a = new MyClass; var_dump($a instanceof MyClass); var_dump($a instanceof NotMyClass); ?>
The above example will output:
bool(true) bool(false)
instanceof can also be used to determine whether a variable is an instantiated object of a class that inherits from a parent class:
Example #2 Using instanceof with inherited classes
<?php class ParentClass { } class MyClass extends ParentClass { } $a = new MyClass; var_dump($a instanceof MyClass); var_dump($a instanceof ParentClass); ?>
The above example will output:
bool(true) bool(true)
To check if an object is not an instanceof a class, the logical not operator can be used.
Example #3 Using instanceof to check if object is not an instanceof a class
<?php class MyClass { } $a = new MyClass; var_dump(!($a instanceof stdClass)); ?>
The above example will output:
bool(true)
Lastly, instanceof can also be used to determine whether a variable is an instantiated object of a class that implements an interface:
Example #4 Using instanceof for class
<?php interface MyInterface { } class MyClass implements MyInterface { } $a = new MyClass; var_dump($a instanceof MyClass); var_dump($a instanceof MyInterface); ?>
The above example will output:
bool(true) bool(true)
Although instanceof is usually used with a literal classname, it can also be used with another object or a string variable:
Example #5 Using instanceof with other variables
<?php interface MyInterface { } class MyClass implements MyInterface { } $a = new MyClass; $b = new MyClass; $c = 'MyClass'; $d = 'NotMyClass'; var_dump($a instanceof $b); // $b is an object of class MyClass var_dump($a instanceof $c); // $c is a string 'MyClass' var_dump($a instanceof $d); // $d is a string 'NotMyClass' ?>
The above example will output:
bool(true) bool(true) bool(false)
instanceof does not throw any error if the variable being tested is not an object, it simply returns FALSE
. Constants, however, are not allowed.
Example #6 Using instanceof to test other variables
<?php $a = 1; $b = NULL; $c = imagecreate(5, 5); var_dump($a instanceof stdClass); // $a is an integer var_dump($b instanceof stdClass); // $b is NULL var_dump($c instanceof stdClass); // $c is a resource var_dump(FALSE instanceof stdClass); ?>
The above example will output:
bool(false) bool(false) bool(false) PHP Fatal error: instanceof expects an object instance, constant given
There are a few pitfalls to be aware of. Before PHP version 5.1.0, instanceof would call __autoload() if the class name did not exist. In addition, if the class was not loaded, a fatal error would occur. This can be worked around by using a dynamic class reference, or a string variable containing the class name:
Example #7 Avoiding classname lookups and fatal errors with instanceof in PHP 5.0
<?php $d = 'NotMyClass'; var_dump($a instanceof $d); // no fatal error here ?>
The above example will output:
bool(false)
The instanceof operator was introduced in PHP 5. Before this time is_a() was used but is_a() has since been deprecated in favor of instanceof. Note that as of PHP 5.3.0, is_a() is no longer deprecated.
See also get_class() and is_a().
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https://secure.php.net/manual/en/language.operators.type.php