interface_exists
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
is_a
(PHP 4 >= 4.2.0, PHP 5)
is_a — Verifica se o objeto é de uma classe ou de sua classe pai
Descrição
bool is_a
( object
$object
, string $class_name
)
Verifica se o dado object é de uma classe ou
de sua classe pai.
Nota:
A função is_a() tornou-se obsoleta no PHP 5 pelo operador instanceof.
Parâmetros
-
object -
The tested object
-
class_name -
The class name
Valor Retornado
Returns TRUE if the object is of this class or has this class as one of
its parents, FALSE otherwise.
Exemplos
Exemplo #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";
}
?>
Exemplo #2 Using the instanceof operator in PHP 5
<?php
if ($WF instanceof WidgetFactory) {
echo 'Yes, $WF is a WidgetFactory';
}
?>
Veja Também
- get_class() - Retorna o nome da classe de um objeto
- get_parent_class() - Recupera o nome da classe pai para o objeto ou classe
- is_subclass_of() - Verifica se o objeto tem esta classe como uma de suas classes pai
add a note
User Contributed Notes
is_a - [7 notes]
p dot scheit at zweipol dot net ¶
6 years ago
eitan at mosenkis dot net ¶
1 year 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 ¶
7 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($test, "Dog").
This seemed intuitive to me, but did not seem to be documented.
Aron Budinszky ¶
1 year ago
Be careful! Starting in PHP 5.3.7 the behavior of is_a() has changed slightly: when calling is_a() with a first argument that is not an object, __autoload() is triggered!
In practice, this means that calling is_a('23', 'User'); will trigger __autoload() on "23". Previously, the above statement simply returned 'false'.
More info can be found here:
https://bugs.php.net/bug.php?id=55475
Whether this change is considered a bug and whether it will be reverted or kept in future versions is yet to be determined, but nevertheless it is how it is, for now...
martin dunisch ¶
7 years ago
Workaround for older PHP-Versions:
function is_a($anObject, $aClass) {
return get_class($anObject) == strtolower($aClass)
or is_subclass_of($anObject, $aClass);
}
dead dot screamer at seznam dot cz ¶
7 years ago
Why I test if class `A` inherit class `B` or implements interface `C` before I create class `A`?
<?
//That isn't work:
//1. function is_A()
if(is_A('A','B'))$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)$a=new A;
?>
zabmilenko at hotmail dot com ¶
7 years ago
Lazy Instantiation using is_a() and php5
<?php
class ObjectA
{
public function print_line($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 :-)