is_a

(PHP 4 >= 4.2.0, PHP 5)

is_a — Checks 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';
}
?>


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

martin dunisch
13-Feb-2006 10:02


Workaround for older PHP-Versions:



function is_a($anObject, $aClass) {

   return get_class($anObject) == strtolower($aClass)

     or is_subclass_of($anObject, $aClass);

}

dead dot screamer at seznam dot cz
06-Feb-2006 09:44


Why I test if class `A` inherit class `B` or implements interface `C` before I create class `A`?



<?

//That isn't work:



//1. function is_A()

if(is_A('A','B'))$a=new A;

if(is_A('A','C'))$a=new A;



//2. operator instanceOf

if(A instanceOf B)$a=new A;

if(A instanceOf C)$a=new A;

?>

zabmilenko at hotmail dot com
08-Oct-2005 03:18


Lazy Instantiation using is_a() and php5





<?php





class ObjectA


{


    public function print_line($text)


    {


        print $text . "\n";


    }


}





class ObjectB


{


    public function ObjectA()


    {


        static $objecta;





        if (!is_a($objecta, 'ObjectA'))


        {


            $objecta = new ObjectA;


        }





        return $objecta;


    }


}





$obj = new ObjectB;


$obj->ObjectA()->print_line('testing, 1 2 3');





?>





In the above example, ObjectA is not instantiated until needed by ObjectB.  Then ObjectB can continually use it's creation as needed without reinstantiating it.  





There are other ways, but I like this one :-)

cesoid at yahoo dot com
06-Oct-2005 05:01


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.

add a note

is_subclass_of

interface_exists

Last updated: Fri, 20 Nov 2009