Which client?

I'm in the early design stages of a program that will have the following features:
a) PostgreSQL database DBMS
b) graphical interface
c) invoice and order tracking
d) report printing / PDF generation
e) multiple concurrent users
f) Linux OR Windows server

The question is, how do I decide what client-side language to use? Java app across the network? PHP scripting/HTML? Java servlets?

Any suggestions?

No client, just browser access to the application. I'd use php, it is excellent end easy, the problems will not come from the language, but from the app's design, I believe.

You can't go wrong with either PHP or Java and a web-based approach, but be extremely careful about security.

If the development team is small, and work together, then PHP is a great choice. Java is sometimes a better choice for a large development team where there is a need for standardization, control, etc...

Mainly, choose what you are more confortable with. As pabloj says, the design of the database and the application is more important than the language used.

I recommend a couple good books:

"Database Design for Mere Mortals" (this gives you a great basic approach to databases in general) and "PostgreSQL Developers Handbook", which can be found at any decent online bookstore.

And, from experience, I will say that reporting is going to be your biggest headache, because there are very few report-building tools in open-source software. Allocate at least 30-40% your time for that alone.

Let me add to my last comment, based on a little more experimentation: actually, complex reporting is not too much trouble if you enable ODBC and/or JDBC. Then, you can use pretty much any of the commercial reporting tools out there, such as Crystal Reports (ODBC), even Microsoft Access, or all kinds of Java reporting tools, which can connect to JDBC.

Also, there is an interesting open source reporting tool available at http://datavision.sourceforge.net/.

Don't spend too much time trying to do serious reporting with HTML, because it is a real pain to generate good printable output.

Hey, thanks very much for the extra comments, and the link! I've started a couple of projects now (and am starting to make a little cash from them), but unfortunately I've been using MSAccess.
I'd love to use Java and PostgreSQL, and started a preliminary design last week, but couldn't find an easy way to do reporting - this ought to help a great deal. The SQL is easy, the Java stuff isn't bad, but reporting was going to be a pain.

Thanks again!