no.php: Transparent reverse proxy written in PHP

This blog post was published 7 years ago and may or may not have aged well. While reading please keep in mind that it may no longer be accurate or even relevant.

The code is at https://github.com/michaelfranzl/no.php

This short, single-file, 80-line PHP script is a simple and fully transparent HTTP(S) reverse proxy written in PHP that allows you to never have to use PHP again for a new project, for example if you are forced to host on a fully 3rd-party-managed server where you can’t do more than run PHP and upload files via FTP. The PHP script simply reads all requests from a browser pointed to it, forwards them (via PHP’s curl library) to a web application listening at another URL (e.g. on a more powerful, more secure, more private, or more capable server in a different data center), and returns the responses transparently and unmodified.

Supports:

  • Regular and XMLHttpRequests (AJAX)
  • All HTTP headers without discrimination
  • GET and POST verbs
  • Content types (HTTP payload) without discrimination
  • Redirects (internal redirects are rewritten to relative URIs)

Does not support (or not tested):

  • HTTP verbs other than GET and POST (but these are usually emulated anyway)
  • HTTP greater than version 1.1 (e.g. reusable connections)
  • Upgrade to websocket (persistent connections)
  • Multipart content type

Usage illustrated by the standard example

You have a non-PHP web application (called the “backend”) listening on https://myapp.backend.com:3000 but due to constraints you must make it available on a shared hosting server called https://example.com/subdir which only supports PHP and can’t be configured at all. On latter server, Apache (or Nginx, doesn’t matter) will usually do the following:

  1. If a URI points to a .php file, this file will be interpreted
  2. If a URI points to a file that is not existing, a 404 status will be returned.

Using no.php, to accomodate the second case, all URIs of the proxied web app (including static files) must be appended to the URI https://example.com/subdir/no.php. For example:

https://example.com/subdir/no.php/people/15/edit

If your backend app supports that extra /subdir/no.php prefix to all paths, you are all set and ready to use no.php. Then:

  1. Simply copy no.php into the subdir directory of example.com
  2. Change $backend_url in no.php to "https://myapp.backend.com:3000"
  3. Point a browser to https://example.com/subdir/no.php

Project status

Experimental. Use only if you know what you are doing.

If you think you found a mistake in this blog post, or would like to suggest an improvement to this blog post, you can write me an e-mail to the address public dot michael at franzl dot name; as subject please use the prefix "Comment to blog post" and append the post title.
 
Copyright © 2023 Michael Franzl