Thank you for your post.
FileMaker, Inc. has registered and reserved port 591, so try changing the port to 591.
Also, turn off Web Sharing in System Preferences, and then turn it on again to reset.
Also, launch a browser and enter http://127.0.0.1 This should take you to the Apache page and confirm it is installed correctly.
If none of these options work, and you have access to another machine, try installing Apache in the default location and see if that works.
Sorry, I don't think you quite understood. The apache is working and I have a full site running there, however I want to be able to put filemaker php files on this server as well, so I've tried to set a two server configuration up in the filemaker server admin. I've installed the web bits of the fm server on the web server but when I try and test the connection it fails because the standard location for the files is where Apple puts it's default web server not in /Library/Apache2/. If I turn on the default web server that connection works. I can't use the standard install because it's 64 bit and some of the software on my site will not work with the 64 bit version.
Basically I'd like to know what the Filemaker server installer does when it configures a webserver to be able to serve fm php files. I'm guessing it installs some plug in and then modifes the conf files to allow the two servers to communicate. But I can't find out how it does that. I need the webserver to continue to work on port 80 - which it seems to do if I share the files directly from the filemaker server.
Thanks for the clarification.
When FileMaker Server 10 installs, there is a zip file, FM_API_for_PHP_Standalone.zip, that is put in the Web Publishing folder. This file should open and extract a FileMaker.php file and a "FileMaker" folder. This file and folder should be put into the following folder:
Hard Disk -> Library -> WebServer -> Documents
...or, into one of the include-path directories in your PHP installation. The default for Mac OS X is /usr/lib/php.
That is the file (and folder) being used by FileMaker Server.