Warning: Use of undefined constant idk - assumed 'idk' (this will throw an Error in a future version of PHP) in /show_cat.php on line 3

Fatal error: Uncaught Error: Call to undefined function mysql_connect() in /funkcje.php:19 Stack trace: #0 /funkcje.php(884): db_connect() #1 /show_cat.php(4): require_once('/funkcje.php') #2 {main} thrown in /funkcje.php on line 19