[man]fopen/man can grab other webpages depending on your version of php
if this file is availible on the web, thats easy...
fopen('http://php.net')
if you file is available over a virtual mapping and whoemver your webserver is running as has access to it
fopen( '/mnt/seatle_office/public_files' )
if you can ftp to the place and you don't mind storing your password in php somewhere then you can use a host of [man]ftp[/man] functions to accomplish the file grab...
read up more on the [man]ftp[/man] functions