How to remove a specific $_GET variable from a URL

Question

I have a website authored in PHP where anytime a user receives an error I will redirect them to a another page (using header(Location:...)) and put the error ID in the URL so that I know which error to display.

E.g. If the user tries to access a product page but that item is no longer available I will redirect back to the category of items they were previously looking at and display an error based on the error ID I have specified in the URL.

www.example.com/view_category.php?product_category_id=4&error_id=5

There are two things I don't like about this approach:

1. It displays the error_id in the URL.
2. if the page is refreshed, the error will still display.

Is there a way to cleanly remove a specific $_GET variable from a URL while leaving the rest of the variables intact AFTER the page is loaded?

I'm thinking maybe it's using modRewrite or a redirect back to the page itself but removing the error_id from the URL or using a $_SESSION variable and avoiding putting the error_id in the URL. Your thoughts?

I really am learning a lot from this community and thought if I posed the question I might be able to learn something new or to get some varied ideas as I'm fairly new to scripting.

Answer 1

One way is to compare the HTTP_REFERER with the SCRIPT_NAME. They'll be the same if the user has hit Refresh.

Answer 2

No, there's no way to do that explicitly - at least not without a page refresh but then you'd lose the data anyway.

You're better off using a temporary session variable.

if ( /* error condition */ )
{
  $_SESSION['last_error_id'] = 5;
  header( 'Location: http://www.example.com/view_category.php?product_category_id=4' );
}

Then, in view_category.php

if ( isset( $_SESSION['last_error_id'] ) )
{
  $errorId = $_SESSION['last_error_id'];
  unset( $_SESSION['last_error_id'] );

  // show error #5
}

Answer 3

First, log the error in your database :)

After that, set a cookie or session variable and then redirect the user to safe page. When that page is loaded, have it check for the variable, display the error, and then delete variable from the cookie or session array.

Answer 4

Quick Hack: You could have also imploded()'d on "&" in the the $_SERVER['QUERY_STRING'] variable to manipulate that string and then explode()'d it back.