PHP simple chat room based on "server push" technology of HTTP long connection_PHP tutorial

The first is the homepage, which contains a text input and an iframe that displays chat content, and a hidden iframe used to submit the form:

Copy code The code is as follows:

//chat.php
header('cache-control: private');
header('Content-Type: text/html; charset =utf-8');
?>




< ;form method="POST" target="say" action="./say.php" onsubmit="submitChat(this)">

The other one is to save the chat content submitted by the user. I simply write the text and do not lock it. This is just a simple version:

Copy code The code is as follows:

$content = trim($_POST['content']);
if ($content) {
$fp = fopen('./chat.txt', 'a');
fwrite($fp, $content . "n");
fclose($fp);
clearstatcache();
}
?>

Next let’s look at the main HTTP long connection part, which is the chat_content.php file:

Copy code The code is as follows:

header('cache-control: private');
header('Content-Type: text/html; charset=utf-8');
//The test sets a 30-second timeout, which is usually set for a longer time.
set_time_limit(30);
//This line is to deal with the BT of IE
echo str_repeat(' ', 256);
ob_flush();
flush();
$fp = new SplFileObject('./chat.txt', 'r+');
$line = 0;
$totalLine = 0;
while (!$fp->eof()) {
$fp->current();
$totalLine++;
$fp->next();
}
$fp->seek($totalLine);
$i = $totalLine - 1;
while (true) {
if (!$fp->eof()) {
if ($content = trim($fp->current ())) {
echo '

';
echo htmlspecialchars($content);
echo "

";
flush();
$fp ->next();
$i++;
}
} else {
$fp->seek($i - 1);
$fp->next() ;
}
{
//Here you can add heartbeat detection and exit the loop
}
usleep(1000);
}
?>

Let me explain it line by line, and it is actually easier to understand:
06. Set a timeout. Since you need to maintain a long HTTP connection, this time must be longer, maybe a few hours, as mentioned above The article also explains that only two of these long HTTP connections can be opened due to browser limitations. In addition, even if you set a never timeout, the configuration file of the server part (such as Apache) may also set the maximum waiting time for HTTP requests, so the effect may not be what you think. Generally, the default may be 15 minutes timeout. If you are interested, you can try to modify it yourself.
09. A section of blank space is output here, mainly because the manual has explained that the IE browser will not directly output the first 256 characters, so we first output some blank space casually to allow the subsequent content to be output. Other browsers may also have settings for other browsers. For details, you can check the description of the frush function in the PHP manual. The next 11 and 12 lines are to force these whitespace characters to be output by the browser.
　13. ~ 20. The main purpose here is to calculate the number of lines in the file so that the content can be read from the end of this line.
The following while loop is an infinite loop, which loops to output the file content. Each time it is judged whether the end of the file is reached. If a user writes to the file, the current detection is definitely not the end of the file, so the line is read out. Output, otherwise move the pointer forward one line and continue looping, waiting 1000 microseconds each time,
　39. If a long connection is maintained, even if the client is disconnected, the server may not know that the client has been disconnected. , so some heartbeat records may need to be done here. For example, each user keeps a heartbeat flag and updates the last heartbeat time every few seconds. When the last time is detected and has not been updated for a long time, this infinite loop is launched and the HTTP connection is closed.
OK, the basic principle is like this. Of course, the performance is not clear. If you are interested, you can try it yourself. Welcome to communicate.

http://www.bkjia.com/PHPjc/320705.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/320705.htmlTechArticleThe first is the homepage, which contains a text input and an iframe for displaying chat content, and a hidden iframe for submission form: Copy the code as follows: ?php //chat.php header(...