虚函数实现php版

<?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; );