public function addCategory(\model\Category $c)
{
$smt = $this->conn->prepare("INSERT INTO " . self::$table . " (\n\t\t\t\t\t\t\t\t\t" . self::$c_name . ", \n\t\t\t\t\t\t\t\t\t" . self::$c_level . ") \n\t\t\t\t\t\t\t\t\t\tVALUES ('" . $c->getCategoryName() . "', \n\t\t\t\t\t\t\t\t\t\t\t'" . $c->getLevel() . "')");
$smt->execute();
}