Codice PHP:

$conex = mysql_connect("localhost", "root", "");
mysql_select_db("test", $conex); 
output
Fatal error: Uncaught Error: Call to undefined function mysql_connect() in C:\xampp\htdocs\sistema-di-prestiti--master\index.php:60 Stack trace: #0 {main} thrown in C:\xampp\htdocs\sistema-di-prestiti--master\index.php on line 60

a cosa si deve?