PHP 物件導向文法細節

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1. $this偽變數

   The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).
   As of PHP 7.0.0 calling a non-static method statically from an incompatible context results in $this being undefined inside the method. Calling a non-static method statically from an incompatible context has been deprecated as of PHP 5.6.0.
   As of PHP 7.0.0 calling a non-static method statically has been generally deprecated (even if called from a compatible context). Before PHP 5.6.0 such calls already triggered a strict notice.

   即

   1. 偽變數$this在object上下文中方法被調用時有效，它是"the calling object"的引用，（通常，the calling object 是方法所屬的對象。但是，也可能是其他對象，如果方法是從次級對象（我的理解是子類對象）的上下文中靜態調用）。
   2. 如果靜態地調用一個非靜態方法，

   例子：
   

    1 <?php 2 class A 3 { 4     function foo() 5     { 6         if (isset($this)) { 7             echo ‘$this is defined (‘; 8             echo get_class($this); 9             echo ")\n";10         } else {11             echo "\$this is not defined.\n";12         }13     }14 }15 16 class B17 {18     function bar()19     {20         A::foo();21     }22 }23 24 error_reporting(E_ALL);25 26 $a = new A();27 $a->foo();28 29 A::foo();　　              //靜態調用非靜態方法30 $b = new B();31 $b->bar();                //從一個incompatibale context靜態調用非靜態方法32 33 B::bar();                 //靜態調用非靜態方法bar(),然後在bar()中再次靜態調用非靜態方法34 ?>

   php 5.5.38執行效果
   
   
   php 7.1.2執行效果
   

    

PHP 物件導向文法細節