Sure, PHP/MySQL has a great following and is used by many people for building dynamic DB-enabled sites. You'll also get some good support for it in applications like GoLive and Dreamweaver.

However, it's more than possible to build interactive web sites with FileMaker Pro. Here are some of your options:

1) Instant Web Publishing. Included with all versions of FileMaker Pro. You basic click a couple check boxes and your web site is up, looking pretty much exactly the way it does in FileMaker itself. By far the easiest way to publish a database online, since you don't need to know a single word of PHP, XML, HTML, CSS or SQL. Basic versions of FileMaker support 5 simultaneous users via IWP and the advanced server allows up to 100 concurrent users.

2) Lasso. Gives you plugins that you can use with GoLive and Dreamweaver. It basically claims to be an easier alterntive to PHP for coding the presentation of your data on the web. Works well with FileMaker.

3) FX.php. Lets you use PHP to present FileMaker Pro-based databases on the web. Free.

4) Custom Web Publishing. Uses XML and/or XSLT style sheets to present information. Included as part of FileMaker.

The advantage of using FileMaker over other DB systems is the incredible ease-of-use and ability to get your system together quickly, without coding.