Validation: Problems with header(Location) in PHP

Hi! I am kind of newbie coming from ASP and I came upon some hindrances, which could be because of not knowing enough of PHP The problem is: I am trying to make a form with good and user-friendly validation. After failure to validate properly some of the fields and going to another page i.e. the <form action="anotherpage.php"> I need to go back to the previos page where the form is. In ASP I would use Response.Redirect and that's it but the header (Location...) in PHP is said that it must be on top of the HTML page before anything else. This doesn't seems to work for me. Does anyone has a solution to this problem? Many thanks in advance! Martin.