I am also curious about the benefits of filemaker over a standard sql database(mysql, postgresql, and sql server or oracle if you want to pay for it)?
Filemaker has a PHP API library, however the documentation is choppy, and the PHP itself is obfuscated. There's a lot of questions you'll run across that you have to figure out entirely for yourself. (Like how to differentiate between AND and OR in your queries, how to do IN-style queries, etc.) I've figured this all out the hard way.
FileMaker isn't designed to replace a standard SQL database - it's an entirely different beast. Think of FileMaker like Microsoft Access. You design your layouts and data in FileMaker and people in your organization connect to it USING the FileMaker Pro application.
However, eventually you want to be able to make some data in FileMaker available over the web. Perhaps you want to publish a schedule on your website and that schedule resides in FileMaker. Or maybe you want people to be able to submit contact requests from the web, and have that start a new project in your issue-tracking FileMaker database.
That's where I come in.
However, that seems to be EVERYONE's experience, which makes me think that it's a good spot to become an expert in, since nobody else wants to go through and learn it.
This article isn't as fully-featured as I might like (I mean, a step-by-step "Here's How Dan Hulton becomes an in-demand contractor" section would be ideal, but hey), but I really like the last section about: "In the chef's kitchen, the knife that can cut anything, cuts nothing."
One of the biggest pains I went through in my current job was setting up FileMaker databases to be read over the internet. I've developed extensive expertise in this area, and was forced to learn from scratch, since there really doesn't exist much in the way of helpful advice on the internet. Apparently, not many people do this.
I'll have to look into this as an avenue.