storing value in session with ctools wizard I have created a multi-step form using Ctools wizard and its working fine.

In multi step form, there is only images, so user will select the image and click on "Continue" button for next step. In the final step, I am showing the result of merged images which are selected in all previous step.

Images are rendering as ajax link in each step and when user click on any image, an ajax callback be executed. 

In each step form load and ajax callback, fid of the images be stored in $_SESSION variable. 

But the problem is that $_SESSION are not updating on the ajax call.

Suppose, there are five images in step 1 in the Ctools multi step form. When step 1 load, I am storing fid of first image into $_SESSION variable and If user click on any images, I am updating the fid in $_SESSION variable.

But, if I check print_r($_SESSION) in next step, its not showing the updated fid. Its only showing fid of the first image in previous step.

If I check ajax callback in fire bug console, its showing correct value of fid and $_SESSION variable.

Please suggest me what I am doing wrong.

Thanks in advance.
you cannot use form_state. every step will have it's own.
cache the date with ctools_object_cache_set