title: How to access constant defined in child class from parent class functions?
body: <p>I saw this example from php.net:</p>
  
  <pre><code>&lt;?php
  class MyClass {
  
       const MY_CONST = "yonder";
  
       public function __construct() {
  
            $c = get_class( $this );
            echo $c::MY_CONST;
       }
  }
  
  class ChildClass extends MyClass {
  
       const MY_CONST = "bar";
  }
  
  $x = new ChildClass(); // prints 'bar'
  $y = new MyClass(); // prints 'yonder'
  ?&gt;
  </code></pre>
  
  <p>But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot.</p>
  
  <p>Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?</p>