我注册成功了，页面上挑错。运行是正常的，什么原因呢。

如题，报错页面显示的代码是：

( ! ) Deprecated: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in E:\php\doAction.php on line 6

Call Stack

#TimeMemoryFunctionLocation

1 0.0004 138232 {main}( ) ..\doAction.php:0

2 0.0004 138808 mysql_connect ( ) ..\doAction.php:6

显示第六行的代码有错，第6行是：
mysql_connect("localhost","root","");

求解。