PHP w/MySQL to replace FileMaker

Hi all. I'm new to PHP and this list. I've been through the website and many of the PHP example scripts and listed example sites, but I haven't seen exactly what I'm looking for. I am developing an interface for MySQL which will replace my FileMaker Pro databases. These databases are used for inventory tracking, purchasing, check registers, accounts payable & receivable, invoicing, and similar retail business activities. I've seen a few examples of sample scripts that contain pieces of what I'm looking for, and they are a help, but before I go through the entire effort of developing this from scratch, I wonder if this has already been done (or is being done) by someone else and I could utilize that code or participate in its development. So is there anything of this sort? Thanks. Lee Howard