In this tutorial, we learn how to use
mod_rewrite module to manage URL rewrites using Apache2. The module allows us to rewrite URLs in a fashionable, that is converting URLs to human-readable paths.
Just think of the last time you visited a blog site to read an article, looking for that particular article to read. When you finally reached the article, the URL looked like this:
That is the work of
mod_rewrite. This tutorial will discuss how to activate
mod_rewrite, create and use the required .htaccess page and finally set up the URL rewrites.
To follow this tutorial, you will need:
- sudo privilege
Step 1 – Installing Apache
In this step, the system required the user to have root privileges.
First, update the system’s package index with the following command:
sudo apt-get update
This will ensure that all packages are up to date.
Then we can now install Apache2 which is the HTTP server and the world most commonly used. Run the following command to install it:
sudo apt-get install apache2
Step 2 – Activating mod_rewrites
Before rewriting our URLs, we need to activate the apache
mod_rewrite module that controls the URL rewrite.
sudo a2enmod rewrite
The command activates the module or—if it is already activated, displays the message, “Module rewrite already enabled”. To put these changes into effect, we need to restart Apache.
sudo service apache2 restart
Step 3 — Setting Up .htaccess
In this step, we will setup a
.htaccess file for managing the rewrite rule. A
.htaccess file makes it possible for us to configure the details of a website without actually altering the server configuration files. For this reason, .htaccess is critical to your web application’s security. The .htaccess file will be hidden within the file because of the period that starts it.
Additionally, the location of the
.htaccess file is very important. This is because the configurations in the .htaccess will affect everything in its directory and the subdirectories.
You can use any text editor of your choice to create the
.htaccess file (NB: the name is only
.htaccess without any other extension or name
Alternatively, the following command will help you create the
.htaccess file. You would have to replace the example.com with the name of your site’s folder.
sudo nano /var/www/html/domain.com/.htaccess
Permitting changes in the .htaccess file
We will need to do some few more changes in our set up and secure a few more settings before we can begin.
First and foremost, let’s allow changes in the .htaccess file. Use your favorite text editor to open the default Apache configuration file or you follow along as we use nano to edit our files.
sudo nano /etc/apache2/sites-enabled/000-default.conf
Edit the your code to look like the following block of code below:
Options Indexes FollowSymLinks MultiViews
allow from all
Now save the file and exit, restart Apache with the following command:
sudo service apache2 restart
The .htaccess file should now be available for all your sites
Now we are set to rewrite our site’s URLs.
Step 4 – Rewriting URLS
The .htaccess file control the entire operation of the URL rewriting.
The URL rewrite commands follow the same pattern:
RewriteRule Pattern Substitution [OptionalFlags]
Short explanation on the rewrite part:
- RewriteRule: specifies the directive
- pattern: a regular expression that matches the desired string
- substitution: path to the actual URL
- OptionalFlags: optional parameters that can modify the rule
When mod_rewrite is not configured for a web application, the application default to using query strings, which are usually appended to the URL using the question mark
? and the delimiter ampersand
&. These query strings are ignored when matching rewrite rules. However, you might need query strings in order pass data between web pages. For instance, a search result page written in PHP may look like the following:
In this example, we would like to simplify this to become:
Simple Replacement Using rewrite
Using a rewrite rule, we could use the following:
RewriteRule ^kofi/30$ search.php?name=kofi&age=30
As it actually maps
search.php?name=kofi&age=30. And that is what we want to achieve.
In this example,
^kofi/30$ is the pattern,
search.php?name=kofi&age=30 is the substitution.
The following special characters were used in the example above:
^indicates the start of the URL, after
$indicates the end of the URL.
kofi/30matches the string “kofi/30”.
search.php?name=kofi&age=30is the actual file that the user accesses.
With this example you should now be able to access
http://domain/kofi/30 in your browser.
We now have a simple rule in our
.htaccess file that can be modified and extended to meet your needs.