So, one day I decided to start a blog. I had available a windows server with IIS 6.0 and I PHP enabled it some time ago. After some looking around I found WordPress was what I wanted to use.  The whole installation works like a charm and with not much hassle. But for SEO reasons, I wanted to use WordPress’s permalink (common structure)  feature. For this to work you need a URL rewrite solution. Apache can use mod_rewrite here, but on IIS we could use for example Helicon’s ISAPI Rewrite Lite. I installed it following Kyle Caulfields manual. But… it didn’t work for me unfortunately.

Update (March 25th, 2011): After updating WordPress from version 2.9.2 to version 3.1 I had this problem again. See the bottom of this page for how I fixed that.

First of all, lets mention I had problems with WordPress 2.9.2 combined with ISAPI_Rewrite3 Lite on IIS 6.0. I don’t know if the problem occurs on other combinations of versions on the previously mentioned software. I’m going to tackle two problems I had with 404’s. First a 404 that came from WordPress and next a 404 from IIS.

404 from WordPress

I installed everything as mentioned above on my development server just as as Kyle Caulfield explained, I added the following code to the httpd.conf file from ISAPI_Rewrite3 Lite:

RewriteEngine on
RewriteBase /

#Exclude javascripts/stylesheets/images etc from rewriting
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

#Perform rewriting
RewriteRule ^(.*)$ index.php?p=$1 [NC,L]

After restarting IIS I could reach my blog’s home page, but as soon as I tried to go to an article I got a 404 page not found from WordPress. What is going wrong here? My assumption was that the rewrite ISAPI plugin was reached because otherwise I’d expected a 404 from IIS here. It must be the rewrite rule. To find out what could be going wrong you need to have some feedback from the system. I added the following code inside {wordpress}/index.php just below the first define statement:

echo "<pre>";
print_r($_SERVER["REQUEST_URI"] );
echo "</pre>";

This piece of code prints out the PHP server REQUEST_URI variable which tells us what the RewriteRule passes on to PHP. I went back to my browser and refreshed my page. What I found was that the rewrite rule was rewriting my URL’s to something like /index.php?p=index.php/my-first-article. Well, that’s not gonna work. The trick is now to fix the rewrite rule just so that it will give me /index.php/my-first-article. I tested that this approach works by placing it in the browser’s location bar and hitting enter. This works, so I know what I should work towards.

Back to the Rewrite Rule:

#Perform rewriting
RewriteRule ^(.*)$ index.php?p=$1 [NC,L]

I saw index.php itself getting picked up by the Regular Expression part ^(.*)$. I’m not going into explaining regex’s here, you could google it :). Let’s update it just so it won’t pick up index.php anymore:

#Perform rewriting
RewriteRule ^(index\.php)*(.*)$ index.php?p=$2 [NC,L]

In short what I’m doing here is creating an extra regex group by surrounding to be matched values with ( and ). This is group 1. Behind it was the old group which now becomes group 2. This 2nd group is the info we need for our rewritten URL. To use this group we need to update the digit in $1 to $2.

After restarting IIS you’ll find out you’ll get the following rewritten URL: /index.php?p=/my-first-article. This is not working since WordPress expects an article number behind ?p=. Lets fix this now:

#Perform rewriting
RewriteRule ^(index\.php)*(.*)$ index.php/$2 [NC,L]

As you can see I changed the ?p= part to a slash. I restarted IIS again and it worked! Time to place my development server version to my live server…

404 from IIS

I did the exact same as mentioned above (installing WordPress and the whole URL rewrite setup) but now on my live server… I again got a… 404… WTF?! This time the 404 came from IIS and not from WordPress. What do I have to fix this time? My assumption now is that the HTTP request doesn’t reach WordPress’s PHP files at all and that the problem lies with IIS and the ISAPI rewrite filter.

I started googling and found that the problem could be the IIS Metabase was somehow corrupted. I installed a tool called IIS MetaBase Explorer. There’s also a Metabase Explorer from Microsoft which you can probably use in the same way.

I first created a backup of the MetaBase with IIS Metabase Explorer (top left button with the red arrow). Now I removed all references  I found to the ISAPI Rewrite filter (see image below) by simply clicking on them and hitting the delete button. If you installed the ISAPI Rewrite filter correctly you should be able to find it in a root folder called Filters and in a folder called filters inside a folder with a number. You can find the correct site by clicking on the numbers and search inside the key/value pairs for you website’s name:

When this was done I removed and reinstalled ISAPI Rewrite3 Lite. Remember to copy the file httpd.conf to your desktop or another place before reinstalling and then place it back in the install dir. I restarted IIS and… voila… you are looking at the result.

Upgrading WordPress 2.9.2 to WordPress 3.1

At some point I updated WordPress from version 2.9.2 to version 3.1. Al went quite well, so I zipped my backup files to store them and probably (hopefully) never to ever need them ;). WordPress was doing fine when just checking my blog on the homepage but then I tried an article… Oh no, not again! I got infinite redirects. After some googling I found people recommending the following plugin: Permalink Fix & Disable Canonical Redirects Pack. It worked for me, so if you fixed this problem before according to my post above, this might help you again. Happy blogging!