Avoiding re-submission of POST forms

One of the functionality that bugs is the dialog you get after submitting a form through a POST request.  More precisely when I want to refresh the page without re-posting.  Altough sometimes re-posting is the desired functionality getting rid of the functionality altogether doesn’t make sense.  What if you could choose when to allow or not reposting form data.

Well recently I found a mehtod that let’s the application do just that decide if a page refresh will prompt to repost or simply do just that…refresh.   The method is called POST/REDIRECT/GET or “PRG” for short.

It’s quite simple, once you’ve established that the re-posting shouldn’t occur.  After a POST request, you issue a Location header REDIRECT along with a 303 response status code.  Then refreshing will issue a GET instead of a POST.  The Status code 303, or more precisely “HTTP/1.1 303 See Other”, means that the response to the request is located somewhere else (pointed by the Location header).

Let’s look at a simple PHP example.

<?php
    /* Check if post array contains data */
    if ( count($_POST) > 1 ) {
          
        /* ... process form here ... */
        
        /* prevent re-posting prompt 
            by redirecting to same url with a 303 status */
        header('Location: '. $_SERVER['PHP_SELF'] , true, 303);
        exit;
        
    } //if
?>

You can also enjoy a Demo