setting request variables

Hi, I have created a small login system for my website. However if a user logs in incorrectly I want to display a error message currently I use the code echo "You could not be logged in! Either the username and password do not match or you have not validated your membership! <br /> Please try again! <br />"; include ("login.php"); However this appears at the top of my website but I want it to appear above the login form so I though I could set a variable in the request called "error" or similar then on the login page just above the login form check for the presence of the request variable "error" and print the appropriate message. So I want to do the following: SET REQUEST VARIABLE ERROR HERE include ("login.php"); But can I set a request variable? i.e in JAVA I would do HttpRequest.setAttribute("error", true); etc.. Any help? Cheers