Safe routing in my own framework using PHP - how

As almost every programmer, I'm writing my own PHP framework for educational purposes. And now I'm looking at the problem with parsing URLs for MVC routing.

Framework will use friendly URLs everywhere. But the question is how to parse them in front controller. For example the link /foo/bar/aaa/bbb may 开发者_开发百科mean "Call the controller's foo action bar and pass parameter aaa with value bbb. But in case someone installs a framework into the subdirectory of the domain root, the directory part should be stripped before determining controller name and action name. And I'm looking for a way to do it safely.

Also I would like to support a fallback case if URL rewriting is not supported on the server.

On different systems different sets of $_SERVER variables are defined. For example, on my local machine from the set of PATH_INFO, REQUEST_URI, REQUEST_URL, ORIG_REQUEST_URI, SCRIPT_NAME, PHP_SELF only REQUEST_URI, SCRIPT_NAME and PHP_SELF are defined. I wonder, if I can rely on them.

Mature frameworks like Symfony or ZF have some compicated algorithms of parsing URLs (at least it seemed to be so). So, I can't just take a part from there for mine.

Two workarounds:

1. Add config variable with url / instalation directory to your application, and strip it from $_SERVER['REQUEST_URI']

2. Make apache rewrite it to get variable

   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteCond %{REQUEST_FILENAME} !-d
   RewriteRule (.*) index.php?myrequest=$1 [QSA,L]
   

I'm currently doing the same research. But everything I see is so complicated that I'll most probably continue using mod_rewrite anyway. After all you end up with the same thing rather you use SEF with PHP or mod_rewrite with apache. Anyway I'll be monitoring this topic.. it's interesting :) Hope the php gurus around here have some more info about this :)

Edit:
It really depends on what you want to do. For my needs I hardcoded most of the pages so they looked SEF. But something like the example below should work as well.

RewriteEngine on
RewriteRule ^/posts/([A-Za-z0-9_\-]+)/([A-Za-z0-9_\-]+)\.html$ posts.php?$1=$2 [NC]

With this example above:

http://localhost/posts/view/23 
http://localhost/posts/delete/23

is equal to:

http://localhost/posts.php?view=23
http://localhost/posts.php?delete=23

It really depends on what exactly you're doing :) The example above should be working but I haven't tested them.

I usually use the following for determining an application base URL path, assuming all your requests always goes through the same gateway script:

$base = dirname($_SERVER['PHP_SELF']);

For your second question, if you want to check if mod_rewrite is enabled, you can use:

if (in_array('mod_rewrite', apache_get_modules())) {
   // rewrite is enabled
}

However, it doesn't necessarily means that RewriteEngine is enabled, so you probably should use an extra condition:

if (in_array('mod_rewrite', apache_get_modules()) &&
    preg_match('/RewriteEngine +On/i', file_get_contents('/path/to/.htaccess'))) {
   // rewrite is enabled and active
}

Maybe you could take PHP_SELF and remove the first n chars where n is the length of SCRIPT_NAME.

Edit: Oops... seems like you can just take PHP_SELF: http://php.about.com/od/learnphp/qt/_SERVER_PHP.htm