is_subclass_of

(PHP 4, PHP 5)

is_subclass_of — 如果此对象是该类的子类，则返回 TRUE

说明

bool is_subclass_of ( object $object , string $class_name )

如果对象 object 所属类是类 class_name 的子类，则返回 TRUE，否则返回 FALSE。

Note: 自 PHP 5.0.3 起也可以用一个字符串来指定 object 参数（类名）。

Example#1 is_subclass_of() 例子


<?php
// define a class
class WidgetFactory
{
  var $oink = 'moo';
}

// define a child class
class WidgetFactory_Child extends WidgetFactory
{
  var $oink = 'oink';
}

// create a new object
$WF = new WidgetFactory();
$WFC = new WidgetFactory_Child();

if (is_subclass_of($WFC, 'WidgetFactory')) {
  echo "yes, \$WFC is a subclass of WidgetFactory\n";
} else {
  echo "no, \$WFC is not a subclass of WidgetFactory\n";
}

if (is_subclass_of($WF, 'WidgetFactory')) {
  echo "yes, \$WF is a subclass of WidgetFactory\n";
} else {
  echo "no, \$WF is not a subclass of WidgetFactory\n";
}

// usable only since PHP 5.0.3
if (is_subclass_of('WidgetFactory_Child', 'WidgetFactory')) {
  echo "yes, WidgetFactory_Child is a subclass of WidgetFactory\n";
} else {
  echo "no, WidgetFactory_Child is not a subclass of WidgetFactory\n";
}
?>

上例将输出：

yes, $WFC is a subclass of WidgetFactory
no, $WF is not a subclass of WidgetFactory
yes, WidgetFactory_Child is a subclass of WidgetFactory

参见 get_class()、 get_parent_class() 和 is_a()。

method_exists

is_a

Last updated: Sun, 25 Nov 2007

add a note User Contributed Notes
is_subclass_of

jm
01-Oct-2008 11:02


It would appear that is_subclass_of is case insensitive unlike get_class in php5.


i.e.





<?php


class fooBar {}


class bar extends fooBar {}





assert(get_class(new fooBar()) == "fooBar");


assert(is_subclass_of(new bar(), "foobar") == true);


?>





i run across this while migrating some code from php4 to php5 and the code would only half-the-time break.

Ondra Zizka
13-Oct-2006 08:31


For PHP4:



/** Returns whether specified class is subclass of the other class. */

function is_subclass($sClass, $sExpectedParentClass){

    do if( $sExpectedParentClass === $sClass ) return true;

    while( false != ($sClass = get_parent_class($sClass)) );

    return false;

}

// Test:

class A {} class B extends A {} class C extends B {} echo (int) is_subclass('C', 'A');

gunniboyh at web dot de
20-May-2006 09:16


is_subclass_of() works also with classes between the class of obj and the superclass.



example:

<?php

class A {};

class B extends A {};

class C extends B {};



$foo=new C();

echo ((is_subclass_of($foo,'A')) ? 'true' : 'false');

?>



echoes 'true' .

01-Oct-2005 09:32


this function does not check interfaces, unlike instanceof operator.

youcantryreachingme at REMOVEME dot hotmail dot com
22-Mar-2005 10:15


A bug report at http://pear.php.net/bugs/bug.php?id=2975 indicates that the "is_subclass_of" function can return the error message:



Warning: Unknown class passed as parameter



in the event that the class represented by the second argument hasn't yet been instantiated.

add a note

method_exists

is_a

Last updated: Sun, 25 Nov 2007