<?php/** * 单例模式 * Class Mysql */class  Mysql{    /*     * 存储实例化句柄     */    private static $conn;    /*     * 私有化,防止实例化     */    private function __construct()    {        $this->conn = mysqli_connect(‘localhost‘, ‘root‘, ‘123456‘);    }    /*     * 获取实例     */    public static function getInstance()    {        if (!(self::$conn instanceof self)) {            self::$conn = new self();        }        return self::$conn;    }    /*     * 方式克隆     */    public function __clone()    {        trigger_error(‘不允许对象克隆‘);    }}var_dump(Mysql::getInstance());