Add $_SERVER[‘REDIRECT_URL’] to nginx.

by ,

We have by far the largest RPM repository with dynamic stable NGINX modules and VMODs for Varnish 4.1 and 6.0 LTS. If you want to install NGINX, Varnish, and lots of useful modules for them, this is your one-stop repository to get all performance-related software.
You have to maintain an active subscription in order to be able to use the repository!


As per Apache 2.4 documentation:

REDIRECT_ environment variables are created from the environment variables which existed prior to the redirect. They are renamed with a REDIRECT_ prefix, i.e., HTTP_USER_AGENT becomes REDIRECT_HTTP_USER_AGENT.

You may find some information for the same in documentation, but this gives you wrong idea about it (note that it comes from a comment by a user):

Data type: String
Purpose: The URL path name of the current PHP file, path-info is N/A and excluding URL query string. Includes leading slash.
Caveat: This is before URL rewrites (i.e. it’s as per the original call URL).
Caveat: Not set on all PHP environments, and definitely only ones with URL rewrites.

Which is all the way wrong.

First, REDIRECT_URL is not path to a PHP file. In general it is a path to a URL (URI, that is path starting with forward slash) of originally requested resource.
More importantly, it is a path that you get after all the internal rewrites/redirects (but the last one) take place.

In nginx + PHP-FPM setup, that would be equal to rewritten URL (value of $uri after all the try_files and rewrite directives).

Why is this important?

Some PHP scripts rely on this Apache-only server variable:
One notable software that makes use of it is PrestaShop, or its performance fork – ThirtyBees.

If you’re running those under nginx with PHP-FPM setup, chances are, you will hit this bug or similar.

Without further ado, here’s how to fix Prestashop (ThirtyBees) and emulate $_SERVER['REDIRECT_URL'] for them.

Add $_SERVER['REDIRECT_URL'] to nginx + PHP-FPM (works for any CMS)

Within your main location of nginx server definition, “save” the rewritten URL. Then in the PHP location set it as environmental variable REDIRECT_URL:

location / {
        # ....
        # you may have a bunch of rewrites above which rewrite URL, e.g.:
        #  rewrite ^/([0-9])(-[_a-zA-Z0-9-]*)?(-[0-9]+)?/.+\.jpg$ /img/p/$1/$1$2.jpg last;

        # At the very bottom of this location, put:
        # Now this is for emulating $_SERVER['REDIRECT_URL'] (Apache)!
        set $redirect_url $uri;

location ~ \.php$ {
    # ...
    # some existing stuff you have for defining PHP-FPM socket or port, etc.

    # We pass rewritten URI to PHP. It will be available as $_SERVER['REDIRECT_URL'] 
    fastcgi_param REDIRECT_URL $redirect_url;

In a nutshell, this allows you to emulate some of the Apache behaviours in nginx. As a result, Apache-centric software can run that easy with nginx as well.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.