Warning: Undefined variable $mysql_link in D:\inetpub\webs\punteggiliveit\csain.php on line 231

Fatal error: Uncaught TypeError: mysqli_query(): Argument #1 ($mysql) must be of type mysqli, null given in D:\inetpub\webs\punteggiliveit\csain.php:231 Stack trace: #0 D:\inetpub\webs\punteggiliveit\csain.php(231): mysqli_query() #1 {main} thrown in D:\inetpub\webs\punteggiliveit\csain.php on line 231