public static function addOrRemoveValueFromArray($arrayKey, $value, $add = null) {
		$array = self::getArray ( $arrayKey );
		$_SESSION [$arrayKey] = $array;
		$search = array_search ( $value, $array );
		if ($search === FALSE && $add) {
			$_SESSION [$arrayKey] [] = $value;
			return true;
		} else if ($add !== true) {
			unset ( $_SESSION [$arrayKey] [$search] );
			$_SESSION [$arrayKey] = array_values ( $_SESSION [$arrayKey] );
			return false;
		}
	}