PHP late static bindings lazy binding

Source: Internet
Author: User

The official website says:

As of PHP 5.3.0, PHP implements a feature called late static bindings which can be used To reference the called Class In a context of the static inheritance.

more precisely, late static bindings work by storing the class named in the last "Non-forwarding call". In case of a static method calls, this is the class explicitly named (usually the one on the left of the  :: &nb Sp;operator); In case of non static method calls, it is the class of the object. A "forwarding call" was a static one that was introduced by  self:: , Parent:: ,   static:: , or, if going up in the class Hierarchy, forward_static_call (). The Function get_called_class ()  can be used-retrieve a string with the name of the CAL Led class and  static::  introduces its scope.

This feature is named "Late static bindings" with a internal perspective in mind. "Late binding" comes from the fact that the static:: would not be resolved using the class where the method is defined But it'll rather be computed using runtime information. It was also called a "static binding" as it can being used for (and but isn't limited to) static method calls.

Limitations of Self ::

Static references to the current class as self :: or __class__ is resolved using the class in which th e function belongs, as in where it is defined:

Example #1 self :: usage,

classA { Public Static functionWho () {Echo __class__; }     Public Static functionTest () { self::Who (); }}classBextendsA { Public Static functionWho () {Echo __class__; }}b:: Test ();

Output A.

Late Static Bindings ' usage¶

Late static bindings tries to solve, Limitation by introducing a keyword that references the class it was Initia Lly called at runtime. Basically, a keyword that would allow you to reference B from test () in the previous example. It was decided the not- introduce a new keyword but rather use static the was already reserved.

Example #2 Static:: Simple usage

<?PHPclassA { Public Static functionWho () {Echo __class__; }     Public Static functionTest () {Static:: Who ();//Here comes late Static Bindings    }}classBextendsA { Public Static functionWho () {Echo __class__; }}b::test ();?>

Output B;

Note:

In non-static contexts, the called class would be the class of the object instance. Since $this , would try to call private methods from the same scope, using static:: may give different Results. Another difference is thisstatic:: can only refer to static properties.

Example #3 static:: usage in a non-static context

classA {Private functionfoo () {Echo"Success!\n"; }     Public functionTest () {$this-foo (); Static::foo (); }}classBextendsA {/*foo () would be copied to B, hence its scope would still be A and * the call is successful*/}classCextendsA {Private functionfoo () {/*original method is replaced; the scope of the new one is C*/    }}$b=NewB ();$b-test ();$c=NewC ();$c->test ();//fails

success! success! success!
( ! ) Fatal Error: Call to Private Method C::foo () from context ' A ' In F:\xampp\htdocs\php\phpSyntax\lateStaticBinding . PHP on line 26

More:

Http://cn2.php.net/lsb

Related Article

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.