<?php

/**

Copyright 2009 Google Inc. All Rights Reserved.

**/

// Tracker version.
define("VERSION", "4.4sh");

define("COOKIE_NAME", "__utmmobile");

// The path the cookie will be available to, edit this to use a different
// cookie path.
define("COOKIE_PATH", "/");

// Two years in seconds.
define("COOKIE_USER_PERSISTENCE", 63072000);

// 1x1 transparent GIF
$GIF_DATA = array(
    chr(0x47), chr(0x49), chr(0x46), chr(0x38), chr(0x39), chr(0x61),
    chr(0x01), chr(0x00), chr(0x01), chr(0x00), chr(0x80), chr(0xff),
    chr(0x00), chr(0xff), chr(0xff), chr(0xff), chr(0x00), chr(0x00),
    chr(0x00), chr(0x2c), chr(0x00), chr(0x00), chr(0x00), chr(0x00),
    chr(0x01), chr(0x00), chr(0x01), chr(0x00), chr(0x00), chr(0x02),
    chr(0x02), chr(0x44), chr(0x01), chr(0x00), chr(0x3b)
);

// The last octect of the IP address is removed to anonymize the user.
function getIP($remoteAddress) {
  if (empty($remoteAddress)) {
    return "";
  }

  // Capture the first three octects of the IP address and replace the forth
  // with 0, e.g. 124.455.3.123 becomes 124.455.3.0
  $regex = "/^([^.]+\.[^.]+\.[^.]+\.).*/";
  if (preg_match($regex, $remoteAddress, $matches)) {
    return $matches[1] . "0";
  } else {
    return "";
  }
}

// Generate a visitor id for this hit.
// If there is a visitor id in the cookie, use that, otherwise
// use the guid if we have one, otherwise use a random number.
function getVisitorId($guid, $account, $userAgent, $cookie) {

  // If there is a value in the cookie, don't change it.
  if (!empty($cookie)) {
    return $cookie;
  }

  $message = "";
  if (!empty($guid)) {
    // Create the visitor id using the guid.
    $message = $guid . $account;
  } else {
    // otherwise this is a new user, create a new random id.
    $message = $userAgent . uniqid(getRandomNumber(), true);
  }

  $md5String = md5($message);

  return "0x" . substr($md5String, 0, 16);
}

// Get a random number string.
function getRandomNumber() {
  return rand(0, 0x7fffffff);
}

// Writes the bytes of a 1x1 transparent gif into the response.
function writeGifData() {
  global $GIF_DATA;
  header("Content-Type: image/gif");
  header("Cache-Control: " .
         "private, no-cache, no-cache=Set-Cookie, proxy-revalidate");
  header("Pragma: no-cache");
  header("Expires: Wed, 17 Sep 1975 21:32:10 GMT");
  echo join($GIF_DATA);
}

// Make a tracking request to Google Analytics from this server.
// Copies the headers from the original request to the new one.
// If request containg utmdebug parameter, exceptions encountered
// communicating with Google Analytics are thown.
function sendRequestToGoogleAnalytics($utmUrl) {
  $options = array(
    "http" => array(
        "method" => "GET",
        "user_agent" => $_SERVER["HTTP_USER_AGENT"],
        "header" => ("Accepts-Language: " . $_SERVER["HTTP_ACCEPT_LANGUAGE"]))
  );
  if (!empty($_GET["utmdebug"])) {
    $data = file_get_contents(
        $utmUrl, false, stream_context_create($options));
  } else {
    $data = @file_get_contents(
        $utmUrl, false, stream_context_create($options));
  }
}

// Track a page view, updates all the cookies and campaign tracker,
// makes a server side request to Google Analytics and writes the transparent
// gif byte data to the response.
function trackPageView() {
  $timeStamp = time();
  $domainName = $_SERVER["SERVER_NAME"];
  if (empty($domainName)) {
    $domainName = "";
  }

  // Get the referrer from the utmr parameter, this is the referrer to the
  // page that contains the tracking pixel, not the referrer for tracking
  // pixel.
  $documentReferer = $_GET["utmr"];
  if (empty($documentReferer) && $documentReferer !== "0") {
    $documentReferer = "-";
  } else {
    $documentReferer = urldecode($documentReferer);
  }
  $documentPath = $_GET["utmp"];
  if (empty($documentPath)) {
    $documentPath = "";
  } else {
    $documentPath = urldecode($documentPath);
  }

  $account = $_GET["utmac"];
  $userAgent = $_SERVER["HTTP_USER_AGENT"];
  if (empty($userAgent)) {
    $userAgent = "";
  }

  // Try and get visitor cookie from the request.
  $cookie = $_COOKIE[COOKIE_NAME];

  $visitorId = getVisitorId(
      $_SERVER["HTTP_X_DCMGUID"], $account, $userAgent, $cookie);

  // Always try and add the cookie to the response.
  setrawcookie(
      COOKIE_NAME,
      $visitorId,
      $timeStamp + COOKIE_USER_PERSISTENCE,
      COOKIE_PATH);

  $utmGifLocation = "http://www.google-analytics.com/__utm.gif";

  // Construct the gif hit url.
  $utmUrl = $utmGifLocation . "?" .
      "utmwv=" . VERSION .
      "&utmn=" . getRandomNumber() .
      "&utmhn=" . urlencode($domainName) .
      "&utmr=" . urlencode($documentReferer) .
      "&utmp=" . urlencode($documentPath) .
      "&utmac=" . $account .
      "&utmcc=__utma%3D999.999.999.999.999.1%3B" .
      "&utmvid=" . $visitorId .
      "&utmip=" . getIP($_SERVER["REMOTE_ADDR"]);

  sendRequestToGoogleAnalytics($utmUrl);

  // If the debug parameter is on, add a header to the response that contains
  // the url that was used to contact Google Analytics.
  if (!empty($_GET["utmdebug"])) {
    header("X-GA-MOBILE-URL:" . $utmUrl);
  }
  // Finally write the gif data to the response.
  writeGifData();
}

?><?php

trackPageView();

?>