Reset URL on form submit - php

Question

I have a form that acts as a filter to a list of inventory.
The form works well but I have been using get in order for the user to flip through pages, for example:
Next page
<?php } ?>
I am getting my data from XML and this is the way I've found works best. However, the form to filter is POST and if a user clicks next page and tries to use the filter afterwards(bunch of drop boxes) then It also uses the get-parameters that have been passed to the URL from the link.
Is there a way, that no form submit, It will reset all the parameters?
http://www.website.com/used-cars/?pos=10&q=Model-Corolla%2C&srt=KMDfr
That would be preform submission, and once the form is submitted, it will look like this:
http://www.website.com/used-cars/
And there will be no GET variables for the page to get anymore.

Answer 1

Yes, after you're done with your processing, call
header("Location: /used-cars/");
die();
And it will redirect the user to the wanted page.

Answer 2

First of all, don't just use the default header("Location...") alone, because that would send a 302 Found (previously called: Moved Temporarily) response, which kinda "lies" about the actual behavior (as it still means "The requested resource resides temporarily under a different URI"). Worse yet: if a form uses POST (which most do), a conforming browser should even ask for permission before redirecting, according to HTTP 1.1.
So, to properly reset form URIs with a GET, use 303 See Other instead, which was specifically added for this purpose.
(It's nice to also combine it with a 201 Created response intended to ack. successful form submissions, so adding a
header("HTTP/2.0 201 Created") to the result page is a nice touch.)
But, to address your old comment "Where would I add this php code? I'm not sure where to put it, the form submission reloads the current page." (though you probably figured it out since then ;) ):
You'll have to handle not only two, but at least three, or even four cases (in conditional branches):
You send the form for displaying + submitting.
You receive the the form data, store it somewhere (i.e. "create a new resource", the idea behind 201 Created), and redirect to a clean URI.
To avoid redisplaying the form again as if nothing had happened (or redirecting forever to the same page), you must detect if you have just redirected to yourself...
But, since you've now removed all the inputs from the URI, you must use some other means to keep track of state. Some straightforward ways for that:
a) Redirect to a different URI.
b) Use a PHP session.
And, finally, if needed: reset and display the form again for new inputs.
Here's an example (with 3/b, and a kind of "faked" 4, for simplicity):
session_start();
if (isset($_GET['some_input'])) // Case 2: We got data!
{
file_put_contents("result", $_GET['some_input']);
$_SESSION['redir'] = true;
header("Location: /used-cars/", true, 303);
exit;
}
else if (isset($_SESSION['redir'])) // Case 3: We have redirected!
{
unset($_SESSION['redir']);
http_response_code(201); // Acknowledge receiving the form data.
echo "OK, we have happily processed the last submitted data: ",
file_get_contents("result"), "<br>";
echo "Reload the page to fill the form again!"; // Case 4: Reset...
}
else // Case 1: Send the form...
{
echo <<<_
<form>
<input type="text" name="some_input">
<input type="submit">
</form>
_;
}