Depending on filesize and Last-Modified or Etag (which ever will be available) i'll determine wether or not the file has to be re-downloaded. Then i use (additi

Depending on filesize and Last-Modified or Etag (which ever will be available) i'll determine wether or not the file has to be re-downloaded. Then i use (additionally) md5_file in php to see if it's changed in comparison with our last copy of the file. (This is actually part of a matroesjka doll / onion like mechanism i've built to synchronize data from our servers to mobile devices. Based on global/group/user rights. I'll be publishing a blog post on that later)