php虚方法怎么实现

php虚方法的实现：首先创建一个PHP示例文件；然后通过“d40cdb8e77c4579249701d0225b6afd5x() 的方式调用了 A::x()，那么如果在子类中A::x()被B::x()覆盖，A::y()将会调用B::x()。 

上例的运行结果如下： 

A::x() was called. A::y() was called. --
B::x() was called. A::z() was called.
virtual-function.php

代码如下:

<?php 
class ParentClass { 
static public function say( $str ) { 
static::do_print( $str ); 
} 
static public function do_print( $str ) { 
echo "<p>Parent says $str</p>"; 
} 
} 
class ChildClass extends ParentClass { 
static public function do_print( $str ) { 
echo "<p>Child says $str</p>"; 
} 
} 
class AnotherChildClass extends ParentClass { 
static public function do_print( $str ) { 
echo "<p>AnotherChild says $str</p>"; 
} 
} 
echo phpversion(); 
$a=new ChildClass(); 
$a->say( &#39;Hello&#39; ); 
$b=new AnotherChildClass(); 
$b->say( &#39;Hello&#39; );

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