Safe assumption that either www or public_html exists on *nix boxes?

From: jerrygarciuh (designs_at_no.spam.nolaflash.com)
Date: 11/06/03 

Date: Thu, 6 Nov 2003 09:25:57 -0600

Hi all,

I am developing a web photo album application in PHP for Unix. As part of
this I want to provide a link to open a browser-based FTP session. Given the
variety of ways in which FTP servers can be set up (ie chroot-ing users home
dir or not), it is difficult to open a window to a specific directory.

I am considering using PHP's realpath('.') to get the whole path and the
regexing out everything before the www or public_html directory.

My question to you is this: On posix compliant web server OSes is it a safe
assumption that either public_html or www exist?

Also, if I could do a system call that tells me what the FTP path/root is
for given directory that would be even better.

TIA,

jg