Remember to use if(fileowner(...) === FALSE) instead of if(!fileowner()) or if(fileowner() == FLASE) because if the owner was "root" it would return 0.
(PHP 4, PHP 5)
fileowner — Gets file owner
Gets the file owner.
Path to the file.
Returns the user ID of the owner of the file, or FALSE on failure. The user ID is returned in numerical format, use posix_getpwuid() to resolve it to a username.
Example #1 Finding the owner of a file
$filename = 'index.php';
Upon failure, an E_WARNING is emitted.
Note: The results of this function are cached. See clearstatcache() for more details.
This function only works if the permissions are more less than 666