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copied!<p>Polling is a bit harder than a simple while : just because generally all things you output to the browser will be interpreted when complete. Your example is quite clear :</p> <pre><code>success:function(data) { var json = data; $("#commidwin").append(json['msg']); last_msg_id = json["last_msg_id_db"]; setTimeout("load_msgs()", 1000); }, </code></pre> <p>jQuery will wait until the response is complete to build your <code>data</code> variable and then will call your success callback.</p> <p>One way to create long-polling is to have a task and a follower :</p> <ul> <li><p>the task is the "infinite" loop, it displays nothing but just catch and trigger events, put in a "box".</p></li> <li><p>the follower is an ajax call made every X seconds, it looks inside the "box" filled by the task, and immediately act inside the page.</p></li> </ul> <p>Here is an example of long-polling, there is no follower, just an event (release) that stops the poll, but you'll get the idea :</p> <pre><code><?php // For this demo if (file_exists('poll.txt') == false) { file_put_contents('poll.txt', ''); } // If this variable is set, a long-polling is starting... if (isset($_GET['poll'])) { // Don't forget to change the default time limit set_time_limit(120); date_default_timezone_set('Europe/Paris'); $time = time(); // We loop until you click on the "release" button... $poll = true; $number_of_tries = 1; while ($poll) { // Here we simulate a request (last mtime of file could be a creation/update_date field on a base) clearstatcache(); $mtime = filemtime('poll.txt'); if ($mtime > $time) { $result = htmlentities(file_get_contents('poll.txt')); $poll = false; } // Of course, else your polling will kill your resources! $number_of_tries++; sleep(1); } // Outputs result echo "Number of tries : {$number_of_tries}<br/>{$result}"; die(); } // Here we catch the release form if (isset($_GET['release'])) { $data = ''; if (isset($_GET['data'])) { $data = $_GET['data']; } file_put_contents('poll.txt', $data); die(); } ?>  <input id="poll" type="button" value="Click me to start polling" /> <br/><br/> Give me some text here : <br/> <input id="data" type="text" /> <br/>  <input id="release" type="button" value="Click me to release polling" disabled="disabled" /> <br/><br/> Result after releasing polling : <div id="result"></div> <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script> <script type="text/javascript"> // Script to launch polling $('#poll').click(function() { $('#poll').attr('disabled', 'disabled'); $('#release').removeAttr('disabled'); $.ajax({ url: 'poll.php', data: { poll: 'yes' // sets our $_GET['poll'] }, success: function(data) { $('#result').html(data); $('#poll').removeAttr('disabled'); $('#release').attr('disabled', 'disabled'); } }); }); // Script to release polling $('#release').click(function() { $.ajax({ url: 'poll.php', data: { release: 'yes', // sets our $_GET['release'] data: $('#data').val() // sets our $_GET['data'] } }); }); </script> </code></pre> <h1>Demonstration : <a href="http://home.fuz.org/tests/poll.php" rel="nofollow">here</a>.</h1>

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