Customizing maps "on the fly"

[Stephan Dunning]

Hello,

I currently have about twenty different choropleth layers available for
viewing (one at a time), so I was able to easily hardcode the class names
and layer descriptions for this phase.  However, I'm am now looking to
expand the available data layers to around 300+, so my previous methodology
does not agree with me.  :)  I would actually like to figure out how to
store all my raw data in a database (SQL Server in my case), have users
create a summarized table of data (eg. by state) based on a separate query
interface, then create a new map "on-the-fly" using this newly created
tablular data.

Is there a way to: 1) "join" this new table to an existing shapefile, or
create a new shapefile that references this table?
		  2) use this custom shapefile to then create an "on the
fly" mapfile to feed mapserver?
		  3) utilize some kind of a Lookup Table to dynamically
populate class names for legend labeling?

I'm set up with PHP3/mapscript and using it in the my site which is
currently based on the DM Solutions gmap demo.
I'm running on a Windows NT, IIS sever.
Here's the URL: http://www2.usrds.org/mapserver/gmap/htdocs/gmap75.phtml

Is PHP enough to create the interface I've described?  Are there other
languages I should utilize instead (in addition)?
Any ideas?

Thanks,
Stephan