The first question is; what exactly is URL Rewriting…? Is that the case when you go to http://studioamk.com and you are brought to http://studioamk.com/blog? NO! This is URL Redirecting and not URL Rewriting! Let us start with an example.

The following URL contains a query string parameter (title) for getting a particular blog post.

http://studioamk.com/blog/getpost.php?title=PageTitle

This can be altered to make it more user and search engine friendly URL as follow.

http://studioamk.com/blog/PageTitle

In another word, when you go to http://studioamk.com/blog/HelloWorld, you will at the same page as you entered in address bar of your browser, but at the backend, the web server will work as http://studioamk.com/blog/index.php?title=HelloWorld and will bring contents from that page to you. This is called URL Rewriting and this can be done by the use of a rewrite engine, which is a software that modifies web URL's appearances.

We will use Ionics Isapi Rewrite Filter (IIRF) to implement URL Rewriting feature in IIS, which is an ISAPI filter, similar in functionality to apache mod_rewrite, that dynamically alters a URL based on rules defined in the configuration file. It is an open-sourced software and we can download and use it for Free.

Step-by-step Guide

• In this tutorial, we’ll just define a very simple rewrite rule; "all values after our domain name will pass to the title parameter of a file name called rewrite_test.php". For example, studioamk.com/HelloWorld will be rewritten into studioamk.com/rewrite_test.php?title=HelloWorld.
  

• Normally, rewrite rules in configuration file are defined using Regular Expression (Regex). To get everything after domain as we defined in previous step, we will just capture everything after the first appearance of a slash character, which can be written in Regex as " ^/(.*)$ ".

• " ^ " and " $ " are Start and End symbols. " /(.*) " means everything after a splash. To get values in " (.*) ", we can use $1 variable as we’ve already grouped them by the use of brackets. Then, we’ll pass what we’ve captured, which is already stored in variable $1, to title parameter of the php file.

• After we’ve logically defined the rule or the business logic, we are now going to write it in the configuration file. Go back to the folder where IsapiRewrite4.dll located and create a text file. Then, rename it to IsapiRewrite4.ini. Open the newly created ini file with notepad or any text editor of your choice. Copy and Paste the following line in your ini file.

RewriteRule ^/(.*)$ /rewrite_test.php?title=$1 [I,L]

• As in above rule, "[I,L]" are called modifiers. "[I]" means our rule is case-Insensitive. "[L]" means this rule is the Last rule. In another word, if the user request matches one of our last rules’ pattern, the rewriter will stop after that rule and will not go for remaining rewrite rules (if any).

• Now, we need to work on our php file. Copy and Paste the following code to rewrite_test.php and place it under website or virtual directory where you setup the URL rewriter. Basically, it will display the values store in title parameter.

  $Page = $_GET["title"];
  echo "It works! You were looking for $Page.";
?>

• Now try browsing your site. Any URL you browse will rewrite to rewrite_test.php. You may need to restart IIS service, if rewriter is not loaded in IIS.

Thus, as you observed, defining RewriteRule is the key in URL Rewriting. Without knowing it, you can’t achieve anything. Therefore, please allocate some times to read through the Readme file that comes along with IIRF zip file. If you are already an expert in Regex, it will be just as easy as counting 1-2-3. Alright, that’s it for today and… Good Luck!