Question: I have a project to designing a website to search Zip codes on a digital map.
Somebody advised me to use PHP with postgreSQL or MySQL.

My professor wants me to tell him why I chose this for a mapping site.

The question is... Is there an expertise web language for GIS site ??
What is the difference if I use MySQL or MSsql or even Access if there is a connection to other remote database ??

Thanks

Answer: 
It could be that I'm not entirely understanding your question, but:

MySQL and PHP are fine choices, but the choice is pretty irrelevant as far as I know. You could do this in any language with any db. Whatever you're most comfortable with. Though I do know my friend who studied GIS did most of his projects in Python.

I'm not positive what you're after, and I know University wants you to do things from scratch, but if I was doing this for a project it sounds like extending Google Maps could get you 99% of the way there?
PHP and MySQL are highly available, usually free, have a less-steep learning curve than most and offer (like many languages) exactly what you need.

I've done several mapping projects using google maps, location searches (based on LAT/LON or ZIP codes), interactive mappings and KML data. MySQL and PHP are more than capable.