单例模式连接数据库的方法

<?php

class Db {
    static private $_instance;
    static private $_connectSource;
    private $_dbConfig = array(
        'host' => '127.0.0.1',
        'user' => 'root',
        'password' => '',
        'database' => 'video',
    );

    private function __construct() {
    }

    static public function getInstance() {
        if(!(self::$_instance instanceof self)) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    public function connect() {
        if(!self::$_connectSource) {
            self::$_connectSource = @mysql_connect($this->_dbConfig['host'], $this->_dbConfig['user'], $this->_dbConfig['password']);    

            if(!self::$_connectSource) {
                throw new Exception('mysql connect error ' . mysql_error());
                //die('mysql connect error' . mysql_error());
            }
            
            mysql_select_db($this->_dbConfig['database'], self::$_connectSource);
            mysql_query("set names UTF8", self::$_connectSource);
        }
        return self::$_connectSource;
    }
}
/*$connect = Db::getInstance()->connect();

$sql = "select * from video";
$result = mysql_query($sql, $connect);
echo mysql_num_rows($result);
var_dump($result);*/