Hi,
As PHP is a server scripting language this wouldn't be entirely possible.
You COULD however, store the data input by the user into a temporary table then on first load store a reference number unique to a row in the 'temporary table' to the session and call that for each page.
Alternatively you could have the onclick set on the same page so as the user clicks through the forms different content holders with the second part of the form appear below the stage the user was just on. then it's a case of making the values of the form elements on the form to hold the value of what the user has submitted so this could be changed.
I hope this helps you, if you have any queries with these suggestions please let me know and I'll try to help you further.
Regards,
Ben