title: PHP: self:: vs parent:: with extends
body: <p>I'm wondering what is the difference between using self:: and parent:: when a static child class is extending static parent class e.g.</p>
  
  <pre><code>class Parent {
  
      public static function foo() {
         echo 'foo';
      }
  }
  
  class Child extends Parent {
  
      public static function func() {
         self::foo();
      }
  
      public static function func2() {
         parent::foo();
      }
  }
  </code></pre>
  
  <p>Is there any difference between func() and func2() and if so then what is it ? </p>
  
  <p>Thank you</p>
  
  <p>Regards</p>