How to connect to the database in singleton mode

<?php

class Db {
    static private $_instance;
    static private $_connectSource;
    private $_dbConfig = array(
        &#39;host&#39; => &#39;127.0.0.1&#39;,
        &#39;user&#39; => &#39;root&#39;,
        &#39;password&#39; => &#39;&#39;,
        &#39;database&#39; => &#39;video&#39;,
    );

    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[&#39;host&#39;], $this->_dbConfig[&#39;user&#39;], $this->_dbConfig[&#39;password&#39;]);    

            if(!self::$_connectSource) {
                throw new Exception(&#39;mysql connect error &#39; . mysql_error());
                //die(&#39;mysql connect error&#39; . mysql_error());
            }
            
            mysql_select_db($this->_dbConfig[&#39;database&#39;], self::$_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);*/