The easiest way to pass variables to third page, is to pass them using form on second page.
If you don't want variables values to be edited on second page, so user can only look at what he entered, you can output variables in <input> element with readonly=true and style="border:0 none transparent". So it wil not be seen that variables are shown in input, but will seem that words are simply printed on page, and user wil not be able to change data because of "readonly=true". If you don't want to show values of some variableson second page, but need them retrived on third page, store their values in <input type="hidden"> on second page.
Then just specify yuor third file as action for this form on second page, and receive variable on third page the same way as you received them on second page.