Suggestions needed to get started

[M. Fioretti]

Greetings,

I have to build a new website, with a map section. Users must be able
to say "show me path number X, and all the interest points distant
less than 20 KMs from its starting point", where:

"show me" means generate on demand a png image of the map with all the
          requested data. The image must be printable at the right
          resolution, that is when on paper must be in the exact scale
          (Hmmm, maybe pdf is better for this: which other tools may
          work with Image_GIS to do pdf?)

the map comes from a complete GIS database, scale 1:25000, the same
used for official topographic maps

"path number X" is available as a series of GPS waypoints or is part
of a road already included in the GIS database

those waypoints and all interest points will be stored in a MySql or
PostgreSql database

My question is that obviously, I'd prefer to do the whole website with
existing FOSS applications. Given the specs above, which other
programs/PHP modules/tools do you recommend? I just need to be pointed
in the right direction, so I can download everything, study it and
start coding everything together by myself.

Any feedback is welcome.

Thank you in advance,
      Marco