Submit of a Form needs reload the page to display results

Hi all, I have a problem with form submits. I have an access control form that my users fill to enter to a private web page, this access page saves 2 session variables and shows the result page that it's an php page with several queries to several tables. Well, when i submit my access control form, i get a blank page, if i check the source code in the browser, it shows "Data missing... form post operation.. bla bla....", so i need to reload the web page for showing the correct query results. This is very inconvenient for my users, Any help will be greatly appreciated. Thanks.. Karina Gomez