PHP error "No input file specified" when calling tinyMCE from a symlink

I use tinyMCE with t开发者_Go百科he PHP compressor. I would like to have it in a single folder, used by all the domains needing it on my server, instead of a copy for each site. However, since I know it's not cross-domains, I thought I could put it in a folder that each site could reach through a symlink.

But I'm getting this PHP error:

No input file specified.

I have the impression it has less to do with tinyMCE itself than with the symlink, but I don't have a clue.

Does anyone know?

Thanks!

UPDATE:

After lots of digging, it seems to have to do with Apache. PHP is run through FCGId, and it seems to be a permission error. However I get an error 500 if I run it with mod_php.

SOLUTION:

Putting it as a real answer so the question is not unanswered... See below

I had put tinyMCE in the same folder as my static server, so in another vHost. The issue was a permission conflict; vHosts seem to not work well with one another. Putting the tinyMCE library in a folder outside /home (or /www) and beloging to root has solved the issue: the symlinks work fine on all domains and the PHP compressor does its job. :)