I saw this example from php.net:

<?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'
?>

But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot.

Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?