PHP 面向对象语法细节
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- $this伪变量
即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 $this being undefined inside the method. Calling a non-static method statically from an incompatible context has been deprecated as of PHP 5.6.0.
As of PHP 7.0.0 calling a non-static method statically has been generally deprecated (even if called from a compatible context). Before PHP 5.6.0 such calls already triggered a strict notice.1. 伪变量$this在object上下文中方法被调用时有效,它是"the calling object"的引用,(通常,the calling object 是方法所属的对象。但是,也可能是其他对象,如果方法是从次级对象(我的理解是子类对象)的上下文中静态调用)。
例子:
2. 如果静态地调用一个非静态的方法,
1. 在PHP 5.6.0之前,不论from an incompatible context 或者 from compatible context 静态调用非静态方法都会触发a strict notice,从incompatible context静态调用非静态方法,$this对象是secondary object的引用,如下面例子中的31行,最后输出指明$this指向B类的对象。
2. 在PHP 5.6.0之后,from an incompatible context静态调用一个非静态方法会引发deprecated。其他情况静态调用非静态方法会触发a strict notice。并且from an incompatible context 静态调用一个非静态方法,非静态方法中的$this伪变量保存secondary object的引用。
3. 在PHP 7.0.0之后,不论是从an incompatible context 或者 from compatibel context 静态调用非静态方法,都会引发deprecated。在PHP7.0.0中,from an incompatible context 静态调用非静态方法会导致非静态方法内的$this伪对象是undefined,与PHP 7.0.0之前,$this伪对象是secondary object 的引用不同。
1 <?php 2 class A 3 { 4 function foo() 5 { 6 if (isset($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 B 17 { 18 function bar() 19 { 20 A::foo(); 21 } 22 } 23 24 error_reporting(E_ALL); 25 26 $a = new A(); 27 $a->foo(); //从compatible context调用方法 28 29 A::foo(); //从compatible context 静态调用非静态方法 30 $b = new B(); 31 $b->bar(); //从一个incompatibale context静态调用非静态方法 32 33 B::bar(); //从compatible context 静态调用非静态方法bar(),然后在bar() 从compatible context中再次静态调用非静态方法 34 ?>
php 5.6.30执行效果
php 7.1.2执行效果
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