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PHP : Function Reference : Class/Object Functions : is_a

is_a

Checks if the object is of this class or has this class as one of its parents (PHP 4 >= 4.2.0, PHP 5)
bool is_a ( object object, string class_name )

Example 383. 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 384. Using the instanceof operator in PHP 5

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

Related Examples ( Source code ) » is_a
















Code Examples / Notes » is_a

martin dunisch

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

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;
?>


aidan

This functionality is now implemented in the PEAR package PHP_Compat.
More information about using this function without upgrading your version of PHP can be found on the below link:
http://pear.php.net/package/PHP_Compat


zabmilenko

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

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.


zabmilenko

In the below example, the object and class name need to be reversed.  Sorry.
Wrong:
'ObjectA', $objecta
Right:
$objecta, 'ObjectA'


p dot scheit

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


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call_user_method_array
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class_exists
get_class_methods
get_class_vars
get_class
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is_a
is_subclass_of
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