configuring Mozilla to recognise .php files

[Rob Clack <rob@theclacks.org.uk>]

I'm trying to learn php and have written the first script from the book 
I've bought, but when I try to open it with Mozilla (1.7.3 under Debian 
linux) it doesn't recognise the .php extension so prompts for the 
application to use to open the file.  I assume there's a configuration 
option I've not checked but can't find it.  When I try to search mail 
archives or google for stuff about php I get a zillion hits because so 
many files out there on the net are php files, so far nothing to do with 
the problem I'm experiencing.

Anyone know how I tell Mozilla I want _it_ to open my .php file?

Thanks in advance
Rob Clack