title: Sync files from remote server with php
body: <p>I am trying to create a desktop app with Php to sync files from remote server.<br>
  How can I check whether the file is modified?  </p>
  
  <p>First I thought to check the the modified date, But it may result in unwanted upload and download when the file is new on server. </p>
  
  <p>Let a file named <strong>sample.txt</strong> created in server(modified date:2012-01-24 10:00:00).
  When I tried to sync this on the next day my app will download it(modified date:2012-01-25 11:00:00). After that when the app check the same folder, it will try to upload the same to server since the file modified date is different in server and in my local system.</p>
  
  <p>So How can I track the changed files something like Dropbox does?</p>