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    is_a

    (PHP 4 >= 4.2.0, PHP 5, PHP 7)

    is_a — Checks if the object is of this class or has this class as one of its parents

    Descrierea

    is_a ( mixed $object , string $class_name [, bool $allow_string = false ] ) : bool

    Checks if the given object is of this class or has this class as one of its parents.

    Parametri

    object

    A class name or an object instance.

    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.

    Valorile întoarse

    Returns true if the object is of this class or has this class as one of its parents, false otherwise.

    Exemple

    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';
    }
    ?>

    A se vedea și

    • get_class() - Returns the name of the class of an object
    • get_parent_class() - Retrieves the parent class name for object or class
    • is_subclass_of() - Checks if the object has this class as one of its parents or implements it

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    User Contributed Notes 7 notes

    up
    44
    Ronald Locke
    7 years 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 {};
    ?>

    <?php
    namespace 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.
    up
    33
    Aron Budinszky
    12 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
    13
    p dot scheit at zweipol dot net
    17 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
    up
    7
    cesoid at yahoo dot com
    18 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
    1
    dkrupyanskiy[at]gmail
    6 years 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

    <?php

    class 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));

    ?>
    up
    0
    eitan at mosenkis dot net
    12 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.
    up
    -20
    portugal {at} jawira {dot} com
    8 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)
    ?>
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