Virtual Subdomains Setup - mod_rewrite, .htaccess, php and/or MySQL

Project Description: I run a classified ads type website and I need to setup geographic location virtual subdomains on my server which re-direct invisibly to a php handling script which will serve up the appropriate content for each geographic location. An example of how I want the site to work would be : [login to view URL] - delivering ads and content for new york area [login to view URL] - delivering ads and content for new york area Deliverables ----------------- 1) Relevant .htaccess rules to setup and handle virtual subdomains 2) Sample PHP script to handle the incoming re-directs and serve them appropriately 3) Deliverables can be also be achieved by Database routing as opposed to .htaccess methods Key Requirements ------------------------ 1) The re-directs should be totally invisible and seamless to the user 2) Once in the chosen subdomain (e.g. [login to view URL]) ... all content is displayed relevant to that location and all scripts operate as if this location was the main site. This means no scripts should fail due to directory location errors etc 3) FAST - The virtual subdomains should be very fast with no appreciable overhead due to the re-directs. 4) The virtual subdomain re-directs must function with existing .htaccess re-directs in place currently Skills Required ------------------ 1) ideally someone who has setup a similar functioning virtual subdomain architecture for a classified ads type website 2) Intimate knowledge and experience of .htaccess and mod-rewrite functions 3) Intimate knowledge and experience of php scripts which handle incoming and outgoing virtual subdomain redirects. I am fairly familiar with all of these areas but am looking to shortcut and save myself days of work by getting someone who has done this before and can provide what i need in minutes or a few hours tops ! Standard responses will be ignored. Please respond to the deliverables and requirements specifically. Thank you.