remembering variables between many forms.

Hello friends. Pls excuse me if this is too simple a question. I have a mysql database running with PHG scripts for member registration, find members etc which is running well. Now I want to make a system to send the username and passwords to members if they have lost them. the way I am doing it is : when the user logs in on the 1st page with his email address, I take him to the second page where I ask the favourite question from the database for which he must answer, then I check that the answer is correct in a third page and send his email. My problem is that I do not know how to remember the variable between the 1st and the third page. I can manage between two pages but not between three pages. Can someone help how I can remember the email address between the above three pages? Thanks very much Denis