如何用php查看郵件是否已被閱讀？

       當你在發送郵件時，你或許很想知道該郵件是否被對方已閱讀，下面有段不錯的代碼可以實現此需求，喜歡的朋友可以參考下 

代碼如下:<? error_reporting(0); Header("Content-Type: image/jpeg");  //Get IP if (!empty($_SERVER['HTTP_CLIENT_IP'])) { $ip=$_SERVER['HTTP_CLIENT_IP']; } elseif (!empty($_SERVER['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"; $fh = fopen($myFile, 'a+'); $stringData = $actual_day . ' ' . $actual_hour . ' ' . $ip . ' ' . $browser . ' ' . "rn"; fwrite($fh, $stringData); fclose($fh);  //Generate Image (Es. dimesion is 1x1) $newimage = ImageCreate(1,1); $grigio = ImageColorAllocate($newimage,255,255,255); ImageJPEG($newimage); ImageDestroy($newimage);  ?>