Yes, you have to use MapScript for that matter (theoretically you could avoid MapScript but it depends much on your actual needs).
Although I can't speak for other MapScript flavors, Perl lacks documentation and examples, hence you should avoid it in my opinion. PHP seems to be the most widely used and extensively documented MapScript flavor so you should start by reading its documentation [1] and examples [2]. I'm doing a similar task at the moment and as far as I can tell, you can't add data to an existing set of data. For example, I've tried to add a city to a layer of cities but whenever I added it, all other cities disappeared. Good luck. [1] http://mapserver.gis.umn.edu/docs/reference/phpmapscript-class/referencemanual-all-pages [2] located in mapserver-4.10.0/mapscript/php/examples -- Benoit Myard
