mod_rewrite, php and the .htaccess file

One approach is to rewrite everything to a handling script

RewriteEngine on
RewriteBase /

# only rewrite if the requested file doesn't exist
RewriteCond %{REQUEST_FILENAME} !-s 

# pass the rest of the request into index.php to handle     
RewriteRule ^(.*)$ /index.php/$1 [L]

so if you have a request to http://yourserver/foo/bar/

what you actually get is a request to http://yourserver/index.php/foo/bar - and you can leave index.php to decide what to do with /foo/bar (using $_SERVER['PATH_INFO'] -tom)

You only need to modify .htaccess the first time. All future requests for inexistent files can then be handled in PHP.

You might also find the docs for mod_rewrite useful - but keep it simple or prepare to lose a lot of sleep and hair tracking down obscure errors.

Your PHP should for very obvious reasons not be able to modify .htaccess. Even if you get that to work, I'm not sure if it is wise.

How about using a more abstract setup in regard to mod_rewrite rules? Define your general URL pattern, as you would like to use it. For example:

/object/action/id

Then write a set of rules that reroute HTTP requests to a PHP page, which in turn makes the decision what page is to run (say, by including the relevant PHP script).

RewriteRule ^/(\w+)/?(\w+)?/?(\d+)?$ /index.php?object=$1&action=$2&id=$3 [nocase]

This way you would not have to update .htaccess very often an still be flexible.