<code class="php hljs "><?php
    // 数据库操作类MySQLDB
    class MySQLDB {
        // 声明属性
        private $server;
        private $username;
        private $password;
        public $default_db;
        public $link;
        // 声明构造函数
        public function __construct($server,$username,$password,$default_db) {
            // 设置连接字符串
            $this->server = $server;
            $this->username = $username;
            $this->password = $password;
            $this->default_db = $default_db;
            // 连接数据库
            $this->link = mysql_connect($this->server,$this->username,$this->password);
            if (!$this->link) {
                echo 'database connect failure!';
            }
            // 设置默认的数据库
            $bool = mysql_select_db($this->default_db,$this->link);
            if (!$bool) {
                echo 'Select default_db failure!';
            }
        }
        // 声明析构函数
        public function __destruct() {
            mysql_close($this->link);
        }
    }</code>