Is this possible or am I on drugs :)

I have a web application that needs to generate a report. Said report
requires a lot of calcuations so that hard coding them is a pain.

I would like to set up a view does does all the apropriate selects and
calculations to make writing my report easier. Is it possible to pass a
user supplied parameter to a view? Would a procedure make this easier?

I could write the query in the code to accomplish want I want but I'm
always looking for new and interesting ways to accomplish things. :)

From a general point of view I want to do something like:

select stuff from table where something=UserSuppliedParameter.

Is this possible to do from within Postgres? How would I go about getting
the User Supplied Parameter? How would I pass it using PHP?

Any comments would be apreciated

Shawn