   ::    , 
      .

      ,      .

 " " (::)          PHP.


 ::   

<?php
class MyClass {
   const CONST_VALUE = ' ';
}
echo MyClass::CONST_VALUE;
?>
 ::   

            self  parent. 


  ::   :

<?php
class OtherClass extends MyClass {
   public static $my_static = ' ';

   public static function doubleColon() {
      echo parent::CONST_VALUE . "\n";
      echo self::$my_static . "\n";
   }
}

OtherClass::doubleColon();
?>
    ,   -, 
PHP      ,  -. 
    ,    . 
      ,    .