清除聊天窗口

Question

I have created a chat window using php, ajax, and jquery. It successfully reads and writes to a file called chatlog.html. I have made a button that clears the chat. It works fine, but all of the clients' chats don't clear until someone speaks. How would I fix this?

chat.php is here since I can't format it correctly: http://pastebin.com/AEwjeZ3w

sendchatmsg.php:

<?php
session_start();

if (isset($_SESSION['username'])) {
    $text = $_POST['cmsg'];
    $fp = fopen("chatlog.html", "a");
    fwrite($fp, "<div><b>" . $_SESSION['username'] . "</b>: " . stripslashes(htmlspecialchars($text)) . "<br></div>");
    fclose($fp);
}
?>

clearchat.php:

<?php
    unlink("chatlog.html");
?>

Answer 1

You can write empty file to it when you clear it.

clearchat.php:

$fp = fopen("chatlog.html", "w");
fwrite($fp, " ";
fclose($fp);