get_current_user

to get the username of the process owner (rather than the file owner), you can use:
<?php
$processUser = posix_getpwuid(posix_geteuid());
print $processUser['name'];
?>

On Centos, the Red Hat linux clone, this instruction gives the file's OWNER (the first parameter in instruction 'chown'). It does not reveal the file's GROUP.
get_current_user() does NOT reveal the current process' user's identity.
See: posix_getuid() - Return the real user ID of the current process

The information returned by get_current_user() seems to depend on the platform.
Using PHP 5.1.1 running as CGI with IIS 5.0 on Windows NT, get_current_user() returns the owner of the process running the script, *not* the owner of the script itself.
It's easy to test - create a file containing:
<?php
 echo get_current_user();
?>

Then access it through the browser. I get: IUSR_MACHINE, the Internet Guest Account on Windows, which is certainly not the owner of the script.