How to create a ticket reference number in PHP and mySQL

Question

I'm working on a ticketing system in PHP and mySQL. I have a table support with id as my primary key and AI.

I want to add ticket_number, so that when a ticket is submitted each ticket is assigned a unique number. I can't use mySQL to AI a second field, right?

If I give the first ticket a number, then write a query to lookup the last ticket_number in the DB, then I was thinking of doing something like:

$ticket = 1;
$next = $ticket+1;
echo "ticket number: #".$next;

would this work or is there a better way?

Answer 1

I decided to adapt @Himanshu kumar's answer as follows (as it resolves my orgional question) to use the user's id and the timestamp (both of which I'm using already) as the ticket number:

$user_id = 7; //example from session variable
$cur_date = date('dmyHis'); //timestamp ticket submitted
$ticket = '#'.$user_id.'-'. $cur_date;

This will create create a unique variable that has the user's id and the date and time. I've used seconds to make it more unique. I will then use a query to find all messages/tickets with this ticket.