PHP calling Scope

• Author: laruence ()

• This address: http://www.laruence.com/2012/06/14/2628.html

Yesterday in the YAF Exchange Group, the Prairie classmate criticized me to become lazy, blog for a long time did not update, today just someone in the segmentfalut asked me a question, I also did a simple answer on the micro-Bo, but feel a word is not clear, write a blog number bar.

The problem here, because it is too long, I will not copy it: This is PHP __call and __callstatic in the inheritance will be generated after the bug?

At first glance, this problem is really confusing, but in fact, the root cause of this misunderstanding is: in PHP, the judge is not static or not by ":" (Paamayim_nekudotayim) symbol, but by calling scope.

So, what is calling scope?

In PHP, when a method is called, the object that the $this pointer to is the calling scope at which the method is called. For the following example:

<?phpfoo::bar ();? >

When the bar method is called, it is in a context that does not have a calling scope domain, so this is a static call.

And for the following example:

<?phpclass A {public Function test () {Foo::bar (); }} $a = new A (); $a->test ();

When calling the bar method, in the context of a $ A $ object, that is, the calling scope at this time is a $ A object, so this is not actually a static call.

To verify this conclusion, consider one of the following practical examples:

<?php class Foo {public Function bar () {var_dump ($this);     }} class A {public function test () {Foo::bar (); }} $a = new A (); $a->test ();? >

What does it output?

Object (A) #1 (0) {}

In the call to bar, this seemingly "static" invocation of the call, $this pointer is assigned value, point to a $ A object, then this is static call it?

I cite this example to illustrate this problem, but in practical applications, we try to avoid using "::" to invoke a non-static method, PHP will also give a strict warning for such a call:

Strict Standards:non-static Method Foo::bar () should not being called statically, assuming $this from incompatible context

Maybe someone would say this should be a bug, right? In fact, more should be caused by wrong use, because you invoke a non-static method of a class in the context of a calling scope with a "static form".

So why is PHP so designed? Consider the following example:

<?php Class A {public function __construct () {}} class B extends A {public Function __construct () {   Parent::__construct (); }   }

When we call the constructor of the parent class, we deliberately pass the current scope to the parent class's constructor as calling scope.

Now, do you have a little more understanding of static calls? In the afternoon the company will open the plenary meeting, hurriedly and on, write may be a bit messy, please everyone haihan, hehe, thanks

PHP calling Scope