(Self Submitting) Form Structure

I have a Form that resides right in the middle of some fairly complex CSS created by another person. 
     (I talked him into letting me practice on his code!)

• The Form is called with an include statement
• The Form is actually two pages long, with the second page being created dynamically based on selections in the first page.
• It’s all contained in one php file that submits to itself.

The structure is as follows:

If page 1 submitted
     Check/Sanitize results from Page 1
          If fail set error variables continue on
          If pass
                 Set "Page One Pass" variable and  continue on
If page 2 submitted
     Check/Sanitize results from Page 2
          If fail set error variables and continue on
          If pass give “Thank You”
                 Set variable to prevent Page 2 from drawing
Check for “Thank You” variable, if it doesn’t exist
Check for "Page One Pass" variable, and if it does exist
      Draw Page 2
           Set "Page 2" draw variable
Check for Page 2 and “Thank You” variables, if they don’t exist
     Draw Page1


I was speaking to a programmer friend of mine (who doesn’t work in php), and he suggested that I write sequentially.
Example:
   Draw Page 1
   Check Page 1
   Draw Page 2
   Check Page 2
       If pass give “Thank You"

But I can’t see how to do that without using Functions, and with Globals turned off—it’s kinda’ a pain.
I thought about using nested While Loops, but that seemed more confusing.

I don’t know if what I just wrote is even remotely understandable…but if you can make sense of it, I’d love to hear your thoughts!

Thank You!