rpi alive

server side:

<?php
if(isset($_GET['h']))
{
  $filename="data/".str_replace('.','',$_GET['h']).'.txt';
  if(!file_exists($filename))
  {
    file_put_contents($filename,$_GET['h']);
  }  
  if(isset($_GET['s']))
  {
    file_put_contents($filename, date('YmdHis').'-'.$_GET['h'].': '.$_GET['s']);
    echo 'k.';
  }
  else
  {
    file_put_contents($filename, date('YmdHis').'-'.$_GET['h'].': ');
  }
}
?>

on rpi:
#!/bin/bash
URL="http://yourdomain/rpi.php"
STRING=`uptime`
wget -O - -q $URL"?h=$HOSTNAME&s=$STRING"