PHP Performing a persistent DB check - php

Question

I'm actually trying to create a ( more or less ) instant chat.
There's just one thing left to go, until it's finished. And that's a DB check for new entries every second by PHP itself.
A while loop works great for it, because i can exit it perfectly.
The Problem is, that the "every second" thing isn't working.
I tried a sleep(1), but that causes a 1 minute server freeze, until the script has been completed.
Hope someone can help me, i'm actually frustrated about this problem.
elseif($latestID != 'undefined' && $_POST['returnafter'] == '60')
{
$timeout = '60';
$i = '0';
while ($i != $timeout)
{
$chat_content = "";
$i++;
$getLastID = mysql_query("SELECT id, userid, content, time_posted FROM (SELECT * FROM chat_system ORDER BY id DESC LIMIT 150) chat_system WHERE id > '" . $latestID . "' $extraQuery ORDER BY id ASC");
while ($lastID = mysql_fetch_object($getLastID))
{
$rowID = $lastID->id;
$user_posted_id = $lastID->userid;
$chat_content = $lastID->content;
$chat_posted = $lastID->time_posted;
$getUserData = mysql_query("SELECT username, avatar, loggedIn FROM account_data WHERE account_id=('" . $user_posted_id . "')");
while ($userData = mysql_fetch_object($getUserData))
{
$username = $userData->username;
$useravatar = $userData->avatar;
$loginStatus = $userData->loggedIn;
}
if ($loginStatus == '1')
{
$onlineStatus = '<img src="./images/3DArt/newOnline.png" class="chat_onlineStatus">';
}
else
{
$onlineStatus = '<img src="./images/3DArt/newOffline.png" class="chat_onlineStatus">';
}
if (date('Y-m-d', $chat_posted) == date('Y-m-d'))
{
$time_posted = strftime('Heute, %H:%M', $chat_posted);
}
elseif (date('Y-m-d', $chat_posted) == date('Y-m-d', strtotime("Yesterday")))
{
$time_posted = strftime('Gestern, %H:%M', $chat_posted);
}
elseif (date('Y-m-d', $chat_posted) < date('Y-m-d', strtotime("Yesterday")))
{
$time_posted = strftime("%A, %d %B %Y %H:%M", $chat_posted);
}
if (isset($_POST['parseEmoticons']) && $_POST['parseEmoticons'] == 'true')
{
$chat_content = emoticons($chat_content);
}
$newChatRow.= '<div class="chatRow" id="' . $rowID . '">
<div class="chatRow_container">
<div><img src="' . $useravatar . '" class="chatAvatar">' . $onlineStatus . '<b>' . $username . '</b>
</div>
</div>' . $modActions . '
<div class="chat_mainMsg">
' . $chat_content . '
</div>
<div class="chatTime">' . $time_posted . '</div>
</div>';
}
$content = str_replace(array(
'\r\n',
'\r',
'\n'
) , "<br />", $newChatRow);
if(!empty($chat_content)) { echo $newChatRow; $i = $timeout; return false; }
if(empty($chat_content)) { sleep(1); return true; }
}
}
I think, this informations should be enough. If not, just ask.
EDIT: The request is initialized by Ajax and on success the request repeats.
That's why PHP have to check for 60 seconds.

Answer 1

you should let the clientside decide what messages it "like" to receive.
eg you call your messages.php class - per ajax on the client side and pass a timestamp when the last time was the script requested new messages
example:
ajax interval with 1 second loop call the messages.php?last=123456 and receive all messages that were created after or equal this timestamp. now you update in javascript the last timestamp and so on.
or you use a perfect framework (if possible) that is designed perfectly for your task to solve this.
http://socket.io/ (or js keyword websockets)