<?php
//set these to determine whether form sent correctly
$errorFirstValue = TRUE; //if an error
$errorSecondValue = TRUE; //if an error

if(!empty($_POST['firstValue'])){
$firstValue= $_POST['firstValue'];
$errorFirstValue = FALSE; //no error for firstValue
}

if(!empty($_POST['secondValue'])){
$secondValue= $_POST['secondValue'];
$errorSecondValue = FALSE; //no error for secondValue
}

//If there are any errors on how you want the page filled out send to original form page
if($errorFirstValue && $errorSecondValue){
header("LOCATION: backtowhateveerpageyoucamefrom.php");
exit();
}
else{
$updateTable = "UPDATE table SET firstValue='$firstValue' WHERE secondValue='$secondValue'";
@mysql_query($updateTable);

header('LOCATION: pagetoforward.php?firstValue=' . $firstValue . '&secondValue=' . $secondValue);
exit();
}

?>

What you do is check the information submitted anyway you want (if its supposed to be a specific type or style use your reg exp) then attach the values to the end of the string your having forwarded to and use a $_GET[''] to get them. If the form is filled out incorrectly use an $error or $valid variable or something of that nature to test what should be submitted, and if it is an error or not valid send back to the original form