Visitor tracking with PHP and Redis

index.php

<?

  /**
   * Read about why this script was written at http://blog.toddzusman.com/post/13291374815/visitor-tracking-using-php-and-redis
   */

  // I'm using Predis from https://github.com/nrk/predis
  require '/path/to/predis/lib/Predis/Autoloader.php';
  Predis\Autoloader::register();

  $conf = array();
  $conf['host'] = '127.0.0.1';
  $conf['port'] = 6379;
  $client = new Predis\Client( $conf );

  function debug ( $msg ) {
    if ( false )
      printf( "%s <br />\n", $msg );
  }

  $host = 'tracking.toddzusman.com';
  $hash = $_GET['hash'];
  $day = floor( time()/86400 );

  if ( array_key_exists('r',$_GET) || $_COOKIE['t'] == 'confirmed' ) {

    debug( "Either we've already been redirected or the cookie is already confirmed, so mark this as a page view" );
    $client->hincrby( 'pageviews:'.$hash, $day, 1 );

  }

  if ( isset($_COOKIE['t']) ) {

    debug( 'The cookie has been set [t='.$_COOKIE['t'].']' );

    if ( $_COOKIE['t'] == 'confirmed' ) {

      debug( 'Cookie exists and was already confirmed, so do nothing' );

    } else if ( array_key_exists('r',$_GET) ) {

      debug( "We've already been redirected, so the browser CAN accept cookies" );

      debug( "Setting cookie 't' to confirmed" );
      setCookie( 't', 'confirmed', time()+1576800000, '/', $host, false );

      debug( 'Incrementing the uniques' );
      $client->hincrby( 'unique:'.$hash, $day, 1 );

    } else {

      debug( "Something fishy happened - the cookie is there but not confirmed, but we have't been redirected" );

    }

  } else {

    debug( 'No cookie has been set' );

    if ( array_key_exists('r',$_GET) ) {

      debug( "We've already been redirected, so the browser CANNOT accept cookies" );

      $client->hincrby( 'nocookie:'.$hash, $day, 1 );

    } else {

      debug( 'The cookie has not been attempted, so we need to set it and redirect' );

      debug( "Setting cookie 't' to redirect" );
      setCookie( 't', 'redirect', time()+1576800000, '/', $host, false );

      header( 'Cache-Control: no-cache, must-revalidate' );
      header( 'Expires: Fri, 9 Sep 1988 05:55:00 EST' );
      header( 'Location: /?r=1&hash='.$hash, true, 302 );
      exit;

    }

  }

  header( 'Cache-Control: no-cache, must-revalidate' );
  header( 'Expires: Fri, 9 Sep 1988 05:55:00 EST' );
  header( 'Content-Type: image/gif' );
  echo base64_decode( 'R0lGODlhAQABAIAAAAAAAAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==' );

?>