Quick start guide to mod_rewrite

19 November 2011

The Apache mod_rewrite module turns out to be a very useful tool when you’re building PHP applications. Here’s a simple quick start guide:

First, make sure Apache has the mod_rewrite module installed. In Ubuntu, you can execute this command:

sudo a2enmod rewrite

Make sure that the AllowOverride directive is set to “All” for the folder containing your files. On Ubuntu, it’s under /etc/apache2/sites-enabled/, called 000-default or default-ssl.

Now, create an .htaccess file in your site’s root folder. Here’s an example:

RewriteEngine On
RewriteBase /~snay2/
RewriteRule ^driver-esl/(.*)/(.*)/$ driver-esl-handler.php?driver=$1&flowershop=$2 [QSA]

Some notes:

The bolded sections are the capturing portions of the regex and where I use them in the rewritten URL.
The [QSA] at the end of the line means "query string append": anything in the query string of the original request will get appended to the new query string Apache created on the fly.
Change the RewriteBase to whatever the root URL of your site is. This was the biggest thing that tripped me up.
For some reason, I had problems getting the rewriting to work on an EC2 Ubuntu instance when the URL and the PHP file had the same name. So I called the PHP file driver-esl-handler.php instead.

I’ve set up a simple PHP script at driver-esl-handler.php like this:

<?php
  header('Content-Type: text/plain');
  print_r($_REQUEST);
?>

Now if I go to a URL like this

http://students.cs.byu.edu/~snay2/driver-esl/driver1/fs2/?_domain=rfq&_name=delivery_ready

I get the following response:

Array
(
    [driver] => driver1
    [flowershop] => fs2
    [_domain] => rfq
    [_name] => delivery_ready
)

I found a great cheat sheet for mod_rewrite here. It’s worth perusing if you’re doing anything other than elementary rewriting. You can also read the official Apache docs.