You didn't say which platform you are on, but assuming you have checked and the file is in the directory path you listed above - check the permissions! They must be the same as the overall Admin folder - and I have found that at least on OSX they get messed up easily.
If the permissions are not correct, I recommend you use a command line to fix them. That seems to be the way to get them to "stick" the best..
If the file is NOT in the directory - hopefully you have a backup somewhere!
Hope that helps!
Karen, Thanks so much for your reply, and I did have a problem in permissions in the past just as you describe. In this case however it seemed as if I was stuck in a loop where Filemaker could not initialize PHP.
I'm not that familiar with the terminal but have done a lot of stuff over the years so thought I'd check out the apache config file httpd.conf.
At the bottom of the file where some items added by Filemaker when I installed Filemaker Server originally. I carefully deleted those items restoring the file to it's pre-Filemaker state.
When I went back into Filemaker Server and edited the server deployment, this time it allowed me to deploy the PHP webserver, and it correctly found Apache server and set it up. I went back into httpd.conf and found that Filemaker had added those deleted lines back in, and everything seems to be OK now.
What a happy feeling when things work!