PHP 7.2.0 Beta 3 Released

# is_a

(PHP 4 >= 4.2.0, PHP 5)

is_aChecks if the object is of this class or has this class as one of its parents

### Description

bool is_a ( object $object , string$class_name )

Checks if the given object is of this class or has this class as one of its parents.

### Parameters

object

The tested object

class_name

The class name

### Return Values

Returns TRUE if the object is of this class or has this class as one of its parents, FALSE otherwise.

### Changelog

Version Description
5.3.0 This function is no longer deprecated, and will therefore no longer throw E_STRICT warnings.
5.0.0 This function became deprecated in favour of the instanceof operator. Calling this function will result in an E_STRICT warning.

### Examples

Example #1 is_a() example

<?php
// define a class
class WidgetFactory
{
var
$oink 'moo'; } // create a new object$WF = new WidgetFactory();

if (
is_a($WF'WidgetFactory')) { echo "yes, \$WF is still a WidgetFactory\n";
}
?>

Example #2 Using the instanceof operator in PHP 5

<?php
if ($WF instanceof WidgetFactory) { echo 'Yes,$WF is a WidgetFactory';
}
?>

### User Contributed Notes 6 notes

24
Aron Budinszky
5 years ago
Be careful! Starting in PHP 5.3.7 the behavior of is_a() has changed slightly: when calling is_a() with a first argument that is not an object, __autoload() is triggered!

In practice, this means that calling is_a('23', 'User'); will trigger __autoload() on "23". Previously, the above statement simply returned 'false'.

https://bugs.php.net/bug.php?id=55475

Whether this change is considered a bug and whether it will be reverted or kept in future versions is yet to be determined, but nevertheless it is how it is, for now...
12
p dot scheit at zweipol dot net
10 years ago
At least in PHP 5.1.6 this works as well with Interfaces.

<?php
interface test {
public function
A();
}

class
TestImplementor implements test {
public function
A () {
print
"A";
}
}

$testImpl = new TestImplementor(); var_dump(is_a($testImpl,'test'));
?>

will return true
Ronald Locke
10 months ago
Please note that you have to fully qualify the class name in the second parameter.

A use statement will not resolve namespace dependencies in that is_a() function.

<?php
namespace foo\bar;

class
A {};
class
B extends A {};
?>

<?php
namespace har\var;

use
foo\bar\A;
$foo = new foo\bar\B(); is_a($foo, 'A'); // returns false;
is_a($foo, 'foo\bar\A'); // returns true; ?> Just adding that note here because all examples are without namespaces. eitan at mosenkis dot net 5 years ago As of PHP 5.3.9, is_a() seems to return false when passed a string for the first argument. Instead, use is_subclass_of() and, if necessary for your purposes, also check if the two arguments are equal, since is_subclass_of('foo', 'foo') will return false, while is_a('foo', 'foo') used to return true. cesoid at yahoo dot com 11 years ago is_a returns TRUE for instances of children of the class. For example: class Animal {} class Dog extends Animal {}$test = new Dog();

In this example is_a($test, "Animal") would evaluate to TRUE as well as is_a($test, "Dog").

This seemed intuitive to me, but did not seem to be documented.
-6
portugal {at} jawira {dot} com
2 years ago
I just want to point out that you can replace "is_a()" function with the "instanceof" operator, BUT you must use a variable to pass the class name string.

This will work:
<?php
$object = new \stdClass();$class_name = '\stdClass';

var_dump(is_a($object,$class_name));     // bool(true)
var_dump(is_a($object, '\stdClass')); // bool(true) var_dump($object instanceof $class_name); // bool(true) ?> While this don't: <?php$object
= new \stdClass();
var_dump(\$object instanceof '\stdClass'); // Parse error: syntax error, unexpected ''\stdClass'' (T_CONSTANT_ENCAPSED_STRING)
?>