Uncaught error

permisi saya mau bertanya kenapa kok ada peringatan : Fatal error: Uncaught Error: Call to undefined function mysql_connect() in C:\xampp\htdocs\aplikasi_web_rumah_sakit_sederhana\sisfo_rumah_sakit\konfig.php:21 Stack trace: #0 C:\xampp\htdocs\aplikasi_web_rumah_sakit_sederhana\sisfo_rumah_sakit\index.php(13): include() #1 {main} thrown in C:\xampp\htdocs\aplikasi_web_rumah_sakit_sederhana\sisfo_rumah_sakit\konfig.php on line 21

$server = "localhost"; $user = "root"; $pass = ""; $dbname = "web_rumahsakit";

$base_url = "http://localhost/project/sifo_rumah_sakit/";

if (mysql_connect($server,$user,$pass)){ //echo ":)"; mysql_select_db($dbname) or die("database not found"); }else{ echo ":("; }

?>