/**
  * Méthode d'initialisation de la session utilisateur.
  * Cette méthode vide le contenu de $_SESSION pour remplir les propriété statiques
  * de la classe Session.
  */
 static function Init()
 {
     if (self::$state === false) {
         self::$session = $_SESSION;
         $_SESSION = [];
         if (isset(self::$session['id'], self::$session['first_name'], self::$session['last_name'], self::$session['accountant'])) {
             self::$id = self::$session['id'];
             self::$first_name = self::$session['first_name'];
             self::$last_name = self::$session['last_name'];
             self::$accountant = self::$session['accountant'];
         } else {
             self::$id = null;
             self::$first_name = null;
             self::$last_name = null;
             self::$accountant = null;
         }
         self::$state = true;
     }
 }