I don't do PHP, but don't think that this is a PHP specific problem. By that I mean that I believe that you'd have the same problem regardless of what server side language you are using. The problem is related more to how HTML forms work with the server side program.
Basically, when you submit a form, the form's data is sent to the server, which does whatever with it and then sends back a new page. It sounds like you are sending back the 'same' page, but when you send it back the data from the second page is lost because the server side script isn't sending it back.
So, I believe that your solutions are:
- send the second form info along with the first form info, so that the script can redisplay the data when it resends the page. This could be done by 1) combining both forms into one and letting the PHP program handle both together or call the other program, etc or 2) when a submit button is pressed, having each form make for itself a copy of the other form's data that can be sent (you'd do this with javascript and hidden fields).
Another option (I think the preferred option if you don't want to combine the two forms into one) would be to put the two forms on separate pages. When they submit the user info form, it returns the blank picture submit form on a new page and the user processes that form.
I just re-read your post and the 'back' button part. I think that making this two pages is your best bet. You don't want the user to have to press the 'back' button.