title: php file that checks timestamp
body: <p>i'm trying to check whether my arduino device is still connected to the database from the android device. therefore, i thought that device should update in database 'last connected' with the timestamp whenever it connects. then the php file on a server checks that timestamp and if the timestamp hasn't changed within 10 seconds it should mark the device in database as disconnected.</p>
  
  <p>i have no clue how to create such php file since i never had experience with it. can anyone tell me if that's even possible to do? and if so how should i approach it?</p>
  
  <p>thanks.</p>