[ka-Map-users] Altering class expressions on the fly

[Brandon Plewe]

[Forgive a newbie in over his head]
ka-Map is amazing.  Thanks everyone for developing it and keeping it open.

I am working on an application in which I need to alter the expressions 
of several classes (each has a separate expression, not using CLASSITEM) 
of a layer in response to a text input.  I'm fairly good at javascript 
and php, but it's always a challenge to hack other people's libraries, 
so I'd appreciate some suggestions of a general strategy.  I need to be 
able to:
- preferably, make mapfile variable substitution work in php/mapscript 
and ka-map (all of the expressions are based on one variable)
- if not, use setExpression() in php to alter the mapfile
- turn off caching for the dynamic layers
- regenerate and reload the group images for the changed layers on demand

Is the only way to do these to hack into init.php and the js libraries?  
I'd rather not touch them, so I can upgrade easier.  If it is possible 
to write my own php script called from my own input response function, 
I'd prefer that, but my guess is that the rest of ka-map won't recognize 
the alterations.  If other people are interested in such a thing, what 
would be the most general and flexible approach (I would guess 1: 
variable substitution 2: metadata)?

Thanks for any help you can provide

Brandon Plewe
BYU Geography