Apache, MySQL, and PHP generally have their own error logs. You would want to consult them for errors. Alternatively you could turn on error displaying on pages in osTicket. To do that you would open
/main.inc.php
scroll to line 48 and locate:
#Don't display errors
ini_set('display_errors', 0);
ini_set('display_startup_errors', 0);
change it to:
#Don't display errors
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
Make sure yuo change it back when your done.