Session variables

I am designing a form using sessions in which the user inputs their details on page 1 and after submitting they are directed to page 2 for confirmation. They then have the option of editing their input (ie they are returned to page 1) where their previous input is reflected in the form fields by value ='<?php echo $var ?>' This works fine except if the input type is a drop down box, in which case the default <option> is shown. Is there any way around this? How can I show the user their previous choice in these boxes? Any insights would be appreciated. Steve