問題在哪？Fatal error: Uncaught Error:

define('DB_HOST', 'localhost');

define('DB_USER', 'root');

define('DB_PASS', 'root');

define('DB_NAME', 'it999hk911_26');

    $mysql_connect = @mysql_connect(DB_HOST, DB_USER, DB_PASS);
    mysql_select_db ( DB_NAME, $mysql_connect );
    mysql_query("set names utf8");
 

------------------------------------------------------------------------------    
Fatal error:  Uncaught Error: Call to undefined function mysql_connect() in C:\phpstudy_pro\WWW\admin.php:10 Stack trace: #0 C:\phpstudy_pro\WWW\admin.php(77): moto_brand(NULL) #1 {main}  thrown in C:\phpstudy_pro\WWW\admin.php on line 10

誰可以個幫助一下，問題在哪？