为什么这个 PHP 代码不起作用？

<?php
    class Database
    {
        protected $db_host = "localhost";
        protected $db_user = "root2"; //здесь специально произведена ошибка. Верное выражение - root в данном случае.
        protected $db_pass = "1111";
        protected $db_name = "program";
        protected $mysqli;

        public function connect()
        {
            try
            {
                $this->mysqli = new mysqli($this->db_host, $this->db_user, $this->db_pass, $this->db_name);
            }
            catch(Exception $expection)
            {
                echo 'Connection error: ' . $expection->getMessage();
            }
        }
    }
    $database = new Database;
    $database->connect();
?>

try and catch 不要抛出错误！