DataAsyncBlock (DAB)

<?php

// Start session if one doesn't exist and setup dat packet array.
if(!$_SESSION){ session_start(); }

// Header needed to parse and collect data.
header("Content-Type: application/javascript");
header('P3P: CP="NOI ADM DEV COM NAV OUR STP"');
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past

// Checks for nulls
function isnull($data){ return (isset($data) && !empty($data)) ? false : true; }

// Encodes data for json response.
function utf8_encode_all($dat)
{ 
  if (is_string($dat)) return str_replace("'", ''', str_replace('"', '"', utf8_encode($dat)));
  if (!is_array($dat)) return $dat; 
  $ret = array(); 
  foreach($dat as $i=>$d) $ret[$i] = utf8_encode_all($d); 
  return str_replace("'", ''', str_replace('"', '"', $ret)); 
} 

// Send a response to a webpage.
function response($_callback, $_data, $_err, $_index, $_uuid, $_length)
{
  $_callback = utf8_encode_all($_callback); 
  $_data = utf8_encode_all($_data); 
  $_err = utf8_encode_all($_err);
  $_index = utf8_encode_all($_index);
  $_uuid = utf8_encode_all($_uuid);
  $_length = utf8_encode_all($_length);
  $data = array("s" => $_data, "e" => $_err, "i" => $_index, "u" => $_uuid);
  echo $_callback . "('" . json_encode($data) . "');\n";
  echo "for (var i = 1; i < $_length; i++) {\n" . 
		"\tvar o = document.getElementById('" . $_callback . $_uuid . "' + i);\n" .
		"\to.parentNode.removeChild(o);\n" .
	"}\n";
}

// Process the form
function process()
{
  // Variables
  $id = '';
  $err = '';
  $status = '';

  // Get request query
  $l = (!isnull($_GET['l'])) ? intval($_GET['l']) : '';
  $c = (!isnull($_GET['c'])) ? $_GET['c'] : '';
  $u = (!isnull($_GET['u'])) ? $_GET['u'] : '';
  $d = (!isnull($_GET['d'])) ? $_GET['d'] : '';
  $i = (!isnull($_GET['i'])) ? intval($_GET['i']) . '' : '';
  
  $dataRequestID = 'dat' . $u;

  if(!isset($_SESSION[$dataRequestID])){ $_SESSION[$dataRequestID] = array(''=>''); }

  // Add buffer to array
  $_SESSION[$dataRequestID][$i] = $d;

  // Check if total packets have been captured.
  if(count($_SESSION[$dataRequestID])==$l)
  {

    // Sort array and pop it into one string.
    ksort($_SESSION[$dataRequestID]);
    $arr = implode($_SESSION[$dataRequestID]);

    // Decode all special characters
    $arr = urldecode($arr);

    try
    {
      if(isnull($arr)){ throw new Exception('Fruit is required!'); }
      $status = ucwords($arr);
    }
    catch (Exception $e) 
    {
      $err = $e->getMessage();
    }

    // Write response back.
    response($c, $status, $err, $i, $u, $l);

    // Remove the current session.
    unset($_SESSION[$dataRequestID]);
  }
}  

// Start the process
process();

?>

<script type="text/javascript">

  // Checks for null, undefined objects and empty strings.
  function isnull(o){return (o==undefined||o==null||(typeof(o)=='string'&&o==''))?true:false;}

  // For turning json to objects.
  String.prototype.run = function(){ return (new Function('with(this) { return ' + this + '}' )).call({}); };

  // Encodes data to be sent via querystring.
  function dabsafe(s)
  { 
    return encodeURIComponent(s).replace(/!/g, '%21').replace(/'/g, '%27').replace(/\(/g, '%28').replace(/\)/g, '%29').replace(/\*/g, '%2A').replace(/%20/g, '+');  
  }

  function uuid() {
    return Math.floor((1 + Math.random()) * 0x100000000).toString(16).substring(1);
  }

  var requestCount = 0;

  // The dab sending method.
  function dab(webpage, callback, data) 
  {
    requestCount++;

    // Variables
    var head = document.head || document.getElementsByTagName('head')[0];
    //var buffer = 500;
    var buffer = 500;

    // Encode url
    var m = dabsafe(data);
    var ml = (m.length <= buffer) ? 1 : (Math.floor(m.length / buffer) + 1);
    var u = uuid();

    console.time(u);

    for(var i = 0; i < ml; i++)
    {
      var pos = i * buffer;
      var d = m.substring(pos, pos + buffer);
      //this.jsonp(d, (i+1), ml+1);
      
      // Create script child and append to head
      var s = document.createElement('script');
      s.id = callback + u + (i + 1);
      s.src = webpage + '?format=json&i=' + (i+1) + '&l=' + (ml+1) + '&c=' + callback + '&d=' + d + '&u=' + u;
      head.appendChild(s);
    }
  }

  var responses = new Array();

  // The dab callback
  function dabcallback(d) 
  {
    if (--requestCount == 0) {
      console.timeEnd("requests");
    }
    if(isnull(d)){ return; } 

    // Create data object.
    var s = d.run();

    if(!isnull(s.e))
    { 
      // Alert error message
      alert(s.e);
      return;
    }
    else
    {
      console.timeEnd(s.u);
      console.log(s);
      responses.push(s.s);
    }

    if (requestCount == 0) {
      responses.forEach(function(each) {
        alert(each);
      });
    }
  }

var fruits = 'blackcurrant | redcurrant | gooseberry | tomato | eggplant | guava | ' +
             'lucuma | chili pepper | pomegranate | kiwifruit | grape | cranberry | ' +
             'blueberry | pumpkin | gourd | cucumber | melon | orange | lemon | lime | ' +
             'grapefruit | blackberry | raspberry | boysenberry | pineapple | fig | ' +
             'mulberry | hedge apple | apple | rose hip | strawberry';

//dab('http://yoursite.com/serverside.php', 'dabcallback', fruits);

console.time("requests");

dab('http://127.0.0.1/dab/serverside2.php', 'dabcallback', fruits);
dab('http://127.0.0.1/dab/serverside2.php', 'dabcallback', 'huhu | haha | hoho | hyhy');
dab('http://127.0.0.1/dab/serverside2.php', 'dabcallback', 'lol | mdr | :o | :p');
dab('http://127.0.0.1/dab/serverside2.php', 'dabcallback', 'a | c | b | d');

</script>

Say you're on domain abc.com, and you want to make a request to domain xyz.com. To do so, you need to cross domain boundaries, a no-no in most of browserland.

The one item that bypasses this limitation is <script> tags. When you use a script tag, the domain limitation is ignored, but under normal circumstances, you can't really DO anything with the results, the script just gets evaluated.

Enter JSONP. When you make your request to a server that is JSONP enabled, you pass a special parameter that tells the server a little bit about your page. That way, the server is able to nicely wrap up its response in a way that your page can handle.