See http://avr.analogic.cz

therm.php

<?php

// some settings first
$rrdtool = "/usr/bin/rrdtool";
$rrd = "temps.rrd";
$png = "temps.png";
$pngUptime = "temps.uptime.png";
$last = "temps.last.txt";

// parse data from request
$temp = isset($_GET['temp']) ? floatval($_GET['temp']) : null;
$uptime = isset($_GET['uptime']) ? intval($_GET['uptime']) : null;

// log data to text file for debug
if(!empty($temp)) {
  file_put_contents($last, date('Y-m-d H:i:s').' '."$temp $uptime\n", FILE_APPEND);
  echo "OK";
}

// if there is no rrd database yet we create it
$start = time();
if (!is_file($rrd)) {
  $cmd = "$rrdtool create $rrd --start ".($start-1)." --step 60 ".
          "DS:temperature:GAUGE:120:-50:80 ".
          "DS:uptime:GAUGE:120:0:U ".
          "RRA:AVERAGE:0.5:1:600 ".
          "RRA:AVERAGE:0.5:6:700 ".
          "RRA:AVERAGE:0.5:24:775 ".
          "RRA:AVERAGE:0.5:288:797 ".
          "RRA:MIN:0.5:1:600 ".
          "RRA:MIN:0.5:6:700 ".
          "RRA:MIN:0.5:24:775 ".
          "RRA:MIN:0.5:288:797 ".
          "RRA:MAX:0.5:1:600 ".
          "RRA:MAX:0.5:6:700 ".
          "RRA:MAX:0.5:24:775 ".
          "RRA:MAX:0.5:288:797 ".
          "RRA:AVERAGE:0.5:1:200";
  echo shell_exec($cmd);
}

// fill with data if we have them
if(!empty($temp)) {
  $cmd = "$rrdtool update $rrd $start:$temp:$uptime";
  echo shell_exec($cmd);
}

// if client is not Arduino but some browser we generate and serve two images 
if(!empty($_SERVER['HTTP_USER_AGENT'])) {
  $cmd = "$rrdtool graph $png ".
    "--title 'Temperature' ".
    "--start 'now-1d' ".
    "--end now ".
    "--imgformat PNG ".
    "--width=600 ".
    "--height=300 ".
    "--lower-limit 0 ".
    "DEF:a=$rrd:temperature:AVERAGE ".
    "'LINE2:a#00b6e4:Temperature in kitchen' ";
  //echo $cmd."<br />";
  shell_exec($cmd);

  echo "<br /><img src='$png'><br /><br />";

  $cmd = "$rrdtool graph $pngUptime ".
    "--title 'Uptime' ".
    "--start 'now-1d' ".
    "--end now ".
    "--imgformat PNG ".
    "--width=600 ".
    "--height=300 ".
    "--lower-limit 0 ".
    "DEF:a=$rrd:uptime:AVERAGE ".
    "'LINE2:a#FE6E3A:Uptime' ";
  //echo $cmd."<br />";
  shell_exec($cmd);
  echo "<br /><br /><img src='$pngUptime'><br /><br />";
}