<?php
    abstract class foo {
     function fooing() {
      echo "Hello, I'm foo :)";
     }
    }
    
    class foo2 extends foo {
     function foo2() {
      $this->fooing();
     }
    }
    
    class foo3 extends foo2 {
     function foo3() {
      $this->foo2();
     }
    }

    $x = new foo3;
    $x->foo3();
    ?>