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mod_rewrite, one simple rule and two stupidly lost hours

Ok, I should admit that mod_rewrite and regular expressions are not my strongest part. Today - as every other day I realize how little knowledge I have. Actually it's good to have such moments. I lost almost two hours fighting with a really really simple mod_rewrite rule in my .htaccess file.

2013-06-05, 12:00:40-2013-06-05, 12:00:40



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Ok, I should admit that mod_rewrite and regular expressions are not my strongest part. Today - as every other day I realize how little knowledge I have. Actually it's good to have such moments. I lost almost two hours fighting with a really really simple mod_rewrite rule in my .htaccess file.

Here is the scenario. I'm working on a ExpressionEngine based project. I'm in charge with the back-end and one of my colleagues is responsible for the front-end stuff. He sliced the design and gave me the templates, .css, .js and image files. I decided to separate the assets from the templates and at the end my directory tree looks like that:

/project
    /config
    /images/
    /public
        / ... here are the .css, .js and image files
    /system
    /templates
        / ... here are the html files
    /themes
    /admin.php
    /index.php
    /.htaccess

Everything works great except the fact that the paths to the things inside the public folder are actually referring the root directory. I.e. I had

<link rel="stylesheet" href="css/gumby.css">

But it had to be:

<link rel="stylesheet" href="public/css/gumby.css">

I didn't want to change every single path so I decided to use mod_rewrite to redirect all those request to the public directory. Even without this problem I had to use .htaccess file, because by default the urls of ExpressionEngine are in format

http://example.com/index.php/template_group/template

But I wanted to be

http://example.com/template_group/template

Anyway, in the EE's user guide I found the exact syntax to accomplish this.

<IfModule mod_rewrite.c>
    RewriteEngine On
    # Removes index.php from ExpressionEngine URLs
    RewriteCond $1 !\.(gif|jpe?g|png)$ [NC]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ /index.php/$1 [L]
</IfModule>

Before to continue I commented all the rules and conditions. I just wanted to have a clear .htaccess file. As you will find out - that was my first mistake.

I know that there is a favicon.png file in the public directory so a request like

http://site.dev/favicon.png

should open the image. Of course I hit the url and saw:

Object not found!
The requested URL was not found on this server. If you entered the URL manually please check your spelling and try again.
If you think this is a server error, please contact the webmaster.

Which is of course normal. I didn't do anything in the .htaccess file and there is no such a file in my root directory. I directly added the following line:

RewriteRule ^(.*)\.(gif|jpg|png|jpeg|css|js|swf)$ /public/$1.$2 [L,NC]

Without to be an expert, I could say - match all the request starting with everything followed by one of those extensions and redirect them to /public folder. At the end I added two flags meaning

  • [L] - no further rules will be processed
  • [NC] - causes the RewriteRule to be matched in a case-insensitive manner

And load the url http://site.dev/favicon.png again and I got

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

WTF! It should work! I tried a lot of things. I added new flags, changed the rule several times. Of course googled the problem. Read a lot of answers, but of course I didn't think about Apache's logs. That was my second mistake. If I had checked the damn file I wouldn't have lost so much time. There were several messages like this one:

Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.

And here is the A-ha moment. mod_rewrite worked as it should. The problem was that once I try to open /favicon.png I was redirected to /public/favicon.png, which is redirected to /public/public/favicon.png and so on and so on. Or at least that's what I think happened. Once I knew the exact problem it was easy to find the solution. I added the following lines, which actually prevent the matching of my super cool rule if the file or directory physically exists.

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

Here is the full .htaccess file

<IfModule mod_rewrite.c>
    RewriteEngine On

    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)\.(gif|jpg|png|jpeg|css|js|swf)$ /public/$1.$2 [L,NC]

    # Removes index.php from ExpressionEngine URLs  
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ /index.php/$1 [L,QSA]

</IfModule>

Conclusion

Check your server's logs before to ask Google :)


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