PHP Multiform Validation and Redirection

Question

I have buy.php with a form where you enter items, quantity, shipping data, etc.

When you click the Submit button, it posts back to buy.php ($_SERVER['PHP_SELF']) and does some data validation.

If there are fields missing or errors, they are highlighted. If everything is correct, I save the $_POST data in $_SESSION variables, then do a header('Location: check.php'), where I display the data so the buyer can check the info one last time before actually buying.

Now, if I'm in check.php and hit the Back button to buy.php so I can change stuff, the browser asks if I want to resend the POST data. I'm trying to avoid that.

Anyone have any good advice or good practices for PHP Multiform validation?

Also, if I had n pages for the user to fill, buy.php, buy2.php, ... buyn.php before check.php would the same ideas still hold?

Answer 1

You could do a redirect to buy.php after saving to the session object, which then does a server redirect to check.php, it would mean when the user clicks back, they're going back to the GET request not the POST request

Answer 2

Yes - I agree with above. I ALWAYS do a redir away from the last post, so clicking back bounces them back without that error OR re-submissions. it also avoids complications. u can always tag the redir link page with a ?m or &m (i.e.: page.php?m) and have this at top of page: (use elseif there after)

if (isset($_GET['m'])) {
  echo 'order placed.';
}
else {
  //...
}

You can have it all on one page too. Just name the submit buttons submit1, submit2, like: (bear in mind if you use an image for submits, it becomes $_POST['submit1_x'] :)

if (isset($_POST[submit1]) {
  //validate + save session data from form1
  //display form 2
} else if(isset($_POST[submit2])) {
  //validate + save session data from form2
  //display form 3
} else {
  //display first form
  //<input type="submit" name="submit1" value="Continue">
}