gistfile1.txt

class _Parent {
    function __construct() {
      
      parent::__construct(); 
      
      $this->self_define(); 
      
    }
    
    function self_define() {
    
      $this->foo = 'hello world'; 
    
    }
    
}

class Child extends _Parent {
    function __construct() {
      
        parent::__construct();
        
    }
    
    function self_define () {
      
      $this->foo = 'Goodbye'; 
      
    }
    
}

$Child = new Child(); 

echo $Child->foo;