Random pictures in Zend

Question

So, I'm quiet new to Zend Framework and stackoverflow (although I read a lot here), so please be gentle!

What I'm trying to do is a digital version of an IAPS test (rate pictures for their arrousal and feeling). I have three sets of pictures and each set contains 72 pictures. Now, if a person starts the online test, a set should be randomly assigned (e.g. set 1 to person A).
Further, each picture in the set should be randomly presented. After the picture is presented, the person has to rate the picture twice (rating-scale 1 to 3, saved into a database). The whole process of presenting the image and the two rating should be limited by 12 seconds.

It looks like this:

[SET 1] & [SET2] & [SET3]
Take random set (note: only one set should be presented)

[PIC 1] & [PIC 2] & [PIC3] & ...
Take random pictures (note: all 72 pictures should be presented in a random order)

[PIC 1] -> Rating 1 -> Rating 2
|................12 seconds ..............|


I'm not sure if this is even possible to code with Zend. I was thinking to use Zend_Session to store the ratings in the session and save it to a database at the end, but I'm not sure if this is the best method (security issues?). Even more headaches causes me the limitation of 12 seconds for the presentation of the picture and the two ratings.

I'd be glad to hear ideas and thoughts.

ps: I'm using Zend Framework Version 1.11.12
edit: Just took out the euqually distrubuted sets. Rule of great numbers says that they will be distributed equally with a great sample...