How do I use PHP to see if a message has been read?

        When you send a message, you may be interested to know whether the message has been read by the other side, there is a good code to achieve this demand, like friends can refer to the next  

The code is as follows: <?  error_reporting (0);  Header ("Content-type:image/jpeg");   //get ip  if (!empty ( $_server[' Http_client_ip '])   {  $ip =$_server[' http_client_ip ']; }  (ElseIf!empty Http_x_forwarded_for '])   {  $ip =$_server[' http_x_forwarded_for ']; }  else  $ip {  server[' remote_addr ']; }   //time  $actual _time = time ();  $actual _day = Date (' Y.M.D ', $ Actual_time);  $actual _day_chart = Date (' d/m/y ', $actual _time);  $actual _hour = Date (' h:i:s ', $actual _time);    //get browser  $browser = $_server[' http_user_agent '];   //log  $myFile = "Log.txt"; &n Bsp $fh = fopen ($myFile, ' A + ');  $stringData = $actual _day. ' ' . $actual _hour. ' ' . $ip. ' ' . $browser. ' ' . "RN";  fwrite ($fh, $stringData);  fclose ($fh);   //generate Image (Es. Dimesion is 1x1)   $newim Age = Imagecreate (1,1);  $grigio = imagecoloralLocate ($newimage, 255,255,255);  imagejpeg ($newimage);  Imagedestroy ($newimage);   ?>