PHP 5.6.0beta1 released

is_a

(PHP 4 >= 4.2.0, PHP 5)

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

Beschreibung

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.

R├╝ckgabewerte

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 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";
}
?>

Beispiel #2 Using the instanceof operator in PHP 5

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

Siehe auch

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User Contributed Notes 4 notes

up
6
Aron Budinszky
2 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=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...
up
1
p dot scheit at zweipol dot net
7 years ago
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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1
cesoid at yahoo dot com
8 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.
up
0
eitan at mosenkis dot net
2 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.
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