Classes/Object 函数
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class_alias

(PHP 5 >= 5.3.0)

class_alias — Creates an alias for a class

说明

bool class_alias ([ string $original [, string $alias ]] )

Creates an alias named alias based on the defined class original. The aliased class is exactly the same as the original class.

参数

original

The original class.

alias

The alias name for the class.

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE.

范例

Example #1 class_alias() example

<?php

class foo { }

class_alias('foo', 'bar');

$a = new foo;
$b = new bar;

// the objects are the same
var_dump($a == $b, $a === $b);
var_dump($a instanceof $b);

// the classes are the same
var_dump($a instanceof foo);
var_dump($a instanceof bar);

var_dump($b instanceof foo);
var_dump($b instanceof bar);

?>

以上例程会输出：

bool(true)
bool(false)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)

参见

Classes/Object 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Creates an alias for a class

用户评论:

adam at adamhahn dot com (06-Sep-2011 08:13)

Something to note,

If the $original class has not yet been defined or loaded, the auto loader will be invoked in order to try and load it.

If the class for which you are trying to create an alias does not exist, or can not be loaded with the auto loader, you will generate a PHP Warning.

programmer-comfreek at hotmail dot com (15-Aug-2011 05:38)

If you defined the class 'original' in a namespace, you will have to specify the namespace(s), too:
<?php
namespace ns1\ns2\ns3;

class A {}

class_alias('ns1\ns2\ns3\A', 'B');
/* or if you want B to exist in ns1\ns2\ns3 */
class_alias('ns1\ns2\ns3\A', 'ns1\ns2\ns3\B');
?>

nicolas dot grekas+php at gmail dot com (31-Dec-2010 09:09)

At first, you might wonder that:
<?php class A {}; class_alias('A', 'B'); ?>

is equivalent to:
<?php class A {}; class B extends A {}; ?>

BUT when derivation creates a new class name - that means, you can then instantiate a new kind of objects - aliasing is just what it says: a synonym, so objects instantiated with the aliased name are of the exact same kind of objects instantiated with the non-aliased name.

See this code for example:
<?php
class A {};
class B1 extends A {};
class_alias('A', 'B2');

$b1 = new B1; echo get_class($b1); // prints B1
$b2 = new B2; echo get_class($b2); // prints A !
?>

nicolas dot grekas+php at gmail dot com (30-Dec-2010 10:41)

class_alias also works for interfaces!

<?php
interface foo {}
class_alias('foo', 'bar');
echo interface_exists('bar') ? 'yes!' : 'no'; // prints yes!
?>

paul [dot] kotets [at] gmail [dot] com (03-Sep-2009 11:43)

This function will appear in PHP 5.3 (at least I can use it with PHP 5.3, build Aug 7 2009 08:21:14)
For older versions of PHP I wrote the next function:

<?php
if (!function_exists('class_alias')) {
    function class_alias($original, $alias) {
        eval('abstract class ' . $alias . ' extends ' . $original . ' {}');
    }
}
?>

Keyword 'abstract' is used for classes, which defines abstract methods.
This function is used in autoload purposes (when I extend classes), so abstract keyword doesn't broke anything for me.