PHP 函数 get_parent_class()

<?php
   class f1 {
      function f1() {
         // implements some logic
      }
   }

   class child extends f1 {
      function child() {
         echo "I'm " , get_parent_class($this) , "'s son \n";
      }
   }

   class child2 extends f1 {
      function child2() {
         echo "I'm " , get_parent_class('child2') , "'s son too \n";
      }
   }

   $foo = new child();
   $bar = new child2();
?>