我在登陸后臺的時候出現了這個

Deprecated: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead

然后我就把數據庫的連接改成了

function?connect(){
$link=mysqli_connect(DB_HOST,DB_USER,DB_PWD)?or?die("數據庫連接失敗Error:".mysqli_errno().":".mysqli_error());
mysqli_set_charset(DB_CHARSET);
mysqli_select_db(DB_DBNAME)?or?die("指定數據庫打開失敗");
return?$link;
}

但是最后登陸后臺時又顯示

Warning: mysqli_set_charset() expects exactly 2 parameters, 1 given in E:\www\hahaha\lib\mysql.func.php on line 9

Warning: mysqli_select_db() expects exactly 2 parameters, 1 given in E:\www\hahaha\lib\mysql.func.php on line 10
指定數據庫打開失敗

我想請教一下這究竟是什么回事??？