Explanation of PHP in "::" can call a non-static method

 What is the calling scope?

In PHP, when calling a method, $ this pointer to the object is the calling scope moment method is called for the following example:

<?php
Foo::bar();
?>

 

When call bar method, in the context of a domain is not calling scope, so this is a static call.

For the following example:

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

 

When call bar method, in the context of a $ a object, that is to say, at this time the calling scope is $ a target, so this really is not a static call.

To verify this conclusion, a practical example consider the following:

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

 

What output do?

object(A)#1 (0) {
}

 

When you call the bar, seemingly "static" call to call, $ this pointer is assigned, and points to the $ a object, that is fairly static call it?

I give this example to illustrate this problem, but we in practical applications, we try to avoid the use of "::" to invoke a non-static method, PHP will give a Strict warning for this call:

1. Strict Standards: Non-static method Foo::bar() should not be called statically, assuming $this from incompatible context

Some might say that this should be considered a bug, right? In fact, more should be caused by incorrect use, because you have a calling scope in the context of a "static form of" call non-static method of a class period.

So why should such a design does PHP 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 are interested in the current scope should be passed to the constructor of the parent class as the calling scope.

:: calling for the use of non-static methods of a class of this operation is wrong, we have to use the correct way to call non-static methods in a class for A :: get () This method, although able to call to Class A non-static method get (), but it will generate an error message

“Strict Standards: Non-static method Foo::bar() should not be called statically, assuming $this from incompatible context”

So, we should try to call non-static methods using the correct way.

Transfer from birds Gebo off:

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