(PHP 4 >= 4.2.0, PHP 5, PHP 7)

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


bool is_a ( object $object , string $class_name [, bool $allow_string = FALSE ] )

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



The tested object


The class name


If this parameter set to FALSE, string class name as object is not allowed. This also prevents from calling autoloader if the class doesn't exist.

Значення, що повертаються

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

Журнал Змін

Версія Опис
5.3.9 Added allow_string parameter
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.


Приклад #1 is_a() example

// define a class
class WidgetFactory
$oink 'moo';

// create a new object
$WF = new WidgetFactory();

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

Приклад #2 Using the instanceof operator in PHP 5

if ($WF instanceof WidgetFactory) {
'Yes, $WF is a WidgetFactory';

Прогляньте Також

  • get_class() - Returns the name of the class of an object
  • get_parent_class() - Retrieves the parent class name for object or class
  • is_subclass_of() - Checks if the object has this class as one of its parents or implements it.

add a note add a note

User Contributed Notes 7 notes

Ronald Locke
5 years 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.

namespace foo\bar;

A {};
B extends A {};

namespace har\var;

$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.
Aron Budinszky
11 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'.

More info can be found here:

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...
p dot scheit at zweipol dot net
15 years ago
At least in PHP 5.1.6 this works as well with Interfaces.

interface test {
  public function

TestImplementor implements test {
  public function
A () {

$testImpl = new TestImplementor();


will return true
cesoid at yahoo dot com
16 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.
4 years ago
Looks like the function signature given in description is wrong. Actually it can take a string  as a first parameter in the case if $allow_string is set to true.

It took some time to find out how the last parameter should be used. Please consider the following example


class Foo{}

printf('autoload has been triggered for %s%s', $classname, PHP_EOL);

var_dump(is_a('UndefinedClassName', Foo::class, true));

eitan at mosenkis dot net
10 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.
portugal {at} jawira {dot} com
7 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:
= 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:
= new \stdClass();
var_dump($object instanceof '\stdClass'); // Parse error: syntax error, unexpected ''\stdClass'' (T_CONSTANT_ENCAPSED_STRING)
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