modify URL with mod_rewrite or hook

Question

i'm trying to achieve the following:

user enters this URL into browser

http://mydomain.com/boston/categoryname/postname/

i then want to get the first "folder" and check whether or not it's "boston" or "newyork" - if yes, then remove this part of the URL, add it as an query-parameter and pass the modified URL on to wordpress:

http://mydomain.com/categoryname/postname/?location=boston

i tried this using apache's mod_rewrite like this:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /

RewriteRule ^(boston|newyork)/(.*)$ /$2?location=$1 [NC,QSA,L]

RewriteRule ^index\.php$ - [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

</IfModule>

in my functions.php i add a filter for request

add_filter('request', 'request_it');
function request_it($query_vars) 
{
    print_r($query_vars);
}

it echos

Array ( 
        [page] => 
        [name] => postname 
        [category_name] => boston/categoryname 
        [location] => boston 
)

so the location gets passed on as a query-parameter but the REQUEST_URI is still /boston/categoryname/postname/ instead of /categoryname/postname/ and wordpress tries to display the wrong content.

how can i really strip the location from the URL?
is mod_rewrite not the right thing to use?
is there a function where WP evaluates the URLs that are passed to it where i can hook into and look for my location?

Answer 1

i fixed it using the apache proxy module:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /

RewriteCond %{QUERY_STRING} !location
RewriteRule ^(boston|newyork)/$ /index.php?location=$1 [NC,QSA,P]

RewriteCond %{QUERY_STRING} !location
RewriteRule ^(boston|newyork)/(.*)$ /$2?location=$1 [NC,QSA,P]

RewriteRule ^index\.php$ - [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

</IfModule>

the [P] option does the trick.

Answer 2

I am on similar turf. See: flexible rewrite 'ramble' URLs with Wordpress And no, [R] or 301 redirects won't get you there. And any regular htaccess rewrite causes trouble, because some part of WPstill helps himself to the original REQUEST_URI (or maybe PATH_INFO).

Did you notice, that you can override $_SERVER variables? (even if that screams hacking)

echo "server".$_SERVER['REQUEST_URI']; //get's you: the original thing
$_SERVER['REQUEST_URI'] = 'banana';
echo "server".$_SERVER['REQUEST_URI']; //gets you: banana

If you figure out something, please post it.