DRandy on "How do you get a form field value into a function variable"

Hi. I added a simple one field form on a page. The user enters a value in that field and submits. Then that value is assigned as a variable in my function before returning. For example, my user enters a zip code in the field. Based on that zip code, my function returns all users in the zip code. I just need to know how to get that value assigned as a variable in my function.

Thanks for your help.