# is_a

(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 $allow_string = FALSE ] ) Checks if the given object is of this class or has this class as one of its parents. ### Parameter-Liste object The tested object class_name The class name allow_string If this parameter set to FALSE, string class name as object is not allowed. This also prevents from calling autoloader if the class doesn't exist. ### Rückgabewerte Returns TRUE if the object is of this class or has this class as one of its parents, FALSE otherwise. ### Changelog Version Beschreibung 5.3.9 Added allow_string parameter 5.3.0 This function is no longer deprecated, and will therefore no longer throw E_STRICT warnings. 5.0.0 This function became deprecated in favour of the instanceof operator. Calling this function will result in an E_STRICT warning. ### Beispiele Beispiel #1 is_a() example  <?php// define a classclass WidgetFactory{ var$oink = 'moo';}// create a new object$WF = new WidgetFactory();if (is_a($WF, 'WidgetFactory')) {  echo "yes, \$WF is still a WidgetFactory\n";}?>  Beispiel #2 Using the instanceof operator in PHP 5  <?phpif ($WF instanceof WidgetFactory) {    echo 'Yes, $WF is a WidgetFactory';}?>  ### Siehe auch • get_class() - Ermittelt den Klassennamen eines Objekts • get_parent_class() - Gibt den Namen der Elternklasse eines Objektes zurück • is_subclass_of() - Prüft ob ein Objekt von der angegebenen Klasse abstammt oder sie implementiert add a note ### User Contributed Notes 7 notes 28 Aron Budinszky 6 years ago  Be careful! Starting in PHP 5.3.7 the behavior of is_a() has changed slightly: when calling is_a() with a first argument that is not an object, __autoload() is triggered!In practice, this means that calling is_a('23', 'User'); will trigger __autoload() on "23". Previously, the above statement simply returned 'false'.More info can be found here:https://bugs.php.net/bug.php?id=55475Whether this change is considered a bug and whether it will be reverted or kept in future versions is yet to be determined, but nevertheless it is how it is, for now...  14 Ronald Locke 1 year ago  Please note that you have to fully qualify the class name in the second parameter. A use statement will not resolve namespace dependencies in that is_a() function. <?php namespace foo\bar;class A {};class B extends A {};?><?phpnamespace har\var;use foo\bar\A;$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. 
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p dot scheit at zweipol dot net
11 years ago
 At least in PHP 5.1.6 this works as well with Interfaces.<?phpinterface 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 
cesoid at yahoo dot com
12 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($test, "Dog").This seemed intuitive to me, but did not seem to be documented.  eitan at mosenkis dot net 6 years ago  As of PHP 5.3.9, is_a() seems to return false when passed a string for the first argument. Instead, use is_subclass_of() and, if necessary for your purposes, also check if the two arguments are equal, since is_subclass_of('foo', 'foo') will return false, while is_a('foo', 'foo') used to return true.  dkrupyanskiy[at]gmail 13 days ago  Looks like the function signature given in description is wrong. Actually it can take a string as a first parameter in the case if$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<?phpclass Foo{}spl_autoload_register(    function($classname){ printf('autoload has been triggered for %s%s',$classname, PHP_EOL);    });var_dump(is_a('UndefinedClassName', Foo::class, true));?> 
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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)?>