<?php

  class MyClass {

    const CONST_VALUE = "A constant value";

  }

  $classname = 'MyClass';
  echo $className::CONST_VALUE."<br>"; // Displays 'A constant value'
  echo MyClass::CONST_VALUE."<br>"; // Displays 'A constant value'

  class OtherClass extends MyClass {

    // Becauase this property is static we can DIRECTLY access it
    public static $my_static = 'Static property';

    public static function doubleColon() {

      echo parent::CONST_VALUE."<br>"; // Displays 'A constant value'
      echo self::CONST_VALUE."<br>"; // Displays 'Static property'

    }

  }

  $classname = 'OtherClass';
  echo $classname::doubleColon();
  OtherClass::doubleColon();


?>