NginX redirect to PHP file if image does not exist on file server

Question

This is what I am trying to do. I am not familiar with Nginx enough to create custom rewrite rules like you can with Apache. It would be greatly appreciated if someone could help me with the Nginx config file! Thank you in advance!

I have an image server running Nginx on port 80 and Apache listening on 8080. What I would like to do is...

when you request an image that does not exist like so:

http://img.server.com/(...ANY DIRECTORY...)/123_4_anyimagename.jpg

it will redirect to

http://img.server.com:8080/image.php?id=123_4_anyimagename

---

Thank you! I almost have this working! I had to put in the root

location ~ \.(gif|jpg|png)${
    root /var/www/mysite.com/httpdocs/;
    try_files $uri @img_proxy
}

location @img_proxy {
    rewrite ^(.*)$ /image.php?id=$1
    proxy_pass      http://127.0.0.1:8080;
}

So in images.php file which is located at

/var/www/mysite.com/httpdocs/image.php

I simply have

<?php echo "test"; ?>  

to see if its working. The problem seems to be php is not kicking in and its just rendering as plain text. Its almost there! Any clues as to where to look?

If I run http://mydomain.com:8080/image.php I get "test" as the output. So I know php is working. What am I overlooking?

Answer 1

Nginx uses the try_files directive to 'see if something exists and fallback to another option' instead of using if statements and rewrites.

Within your server block, create a location block that will match your files (e.g. files ending in jpg, gif, png - add whatever extensions you want). Within that block, you will add your try_files directive. Nginx will try the paths in order - so, you start with the direct path to the image, and then list the path to your php file (but that needs to be proxied, so use a named location instead). Perhaps something like the following:

location ~ \.(gif|jpg|png) {
    try_files $uri @img_proxy;
}

The above essentially amounts to the following: For any files ending in .gif, .jpg, or .png first try the path ($uri), and if it doesn't exist goto @img_proxy.

Now, you need to create a second location @img_proxy that nginx will use if it can't find the actual file. In this you will specify your proxy settings, will also have a rewrite to change the path, and finally will pass the URI to the backend server.

Something like the following (the regex is NOT what you are looking for - it will pass the entire path, not just the file name - you can modify it to suit your needs):

location @img_proxy {
    rewrite ^(.*)$ /image.php?id=$1;
    proxy_pass      http://127.0.0.1:8080;
}

Answer 2

This is an old Post, since other answers did not work for me, then I'm sharing my simple solution with other programmers that have the same problem. The codes are missing redirect or permanent at the end of the rewrite rules :

location ~ \.(gif|jpg|png)${
    root /var/www/mysite.com/httpdocs/;
    try_files $uri @img_proxy;
}

location @img_proxy {
    rewrite ^(.*)$ /image.php?id=$1 redirect;
    proxy_pass      http://127.0.0.1:8080;
}

Or in one line :

location @img_proxy {
    rewrite ^(.*)$ http://127.0.0.1:8080/image.php?id=$1 redirect;
}

Answer 3

cyberx86's answer worked kinda well for me, but I had to remove the proxy_pass line, get rid of a dollar sign, and add some semicolons. The addition to my config is:

    location ~ \.(gif|jpg|png) {
        try_files $uri @img_proxy;
    }

    location @img_proxy {
        rewrite ^(.*)$ /tools/image/?url=$1;
    }