这个问题在这里已经有了答案：

如何在php中不断刷新mysql查询(（1个答案）
昨天关门了。
我有一个网站，这是一个消息传递应用程序。
目前，它通过读取refresh.php文件的输出，每500毫秒刷新一次。
我想知道是否有可能在每次“messages”表更新时调用refresh函数。
大多数答案包括settimeout或setinterval，但我只想在表更新时刷新它，因为上次我的网站因为主机服务器过载而被挂起。
聊天盒（index.php）：

<div id="chatbox">
                <?php
                if ($result = $mysqli->query("SELECT * FROM messages")) {
                    while ($row = $result->fetch_assoc()) {
                        echo formatMessageHTML($row["text"], $row["authorid"], $row["timestamp"], $row["hidden"], $mysqli);
                    }
                    $result->free();
                }
                ?>
            </div>

refresh.php

<?php
include_once "dbconnect.php";
$mysqli = new mysqli("localhost", $username, $password, $database);
if ($result = $mysqli->query("SELECT * FROM messages LIMIT 50")) {
    while ($row = $result->fetch_assoc()) {
            echo formatMessageHTML($row["text"], $row["edited"], $row["authorid"], $row["timestamp"], $row["hidden"], $mysqli);
        }
    }
    $result->free();
function formatMessageHTML($text, $edited, $authorid, $timestamp, $hidden, $mysqli)
{
    $html_message = "";
    if ($hidden == 1) return;
    if (!isset($text) || !isset($authorid) || !isset($timestamp)) return "<div class='msgln'><span class='chat-time'>" . date("g:i A") . "</span> <a class='taglink' href='javascript:insert_mention(\"Unknown\");'><b class='user-name'>Unknown</b></a> Unknown<br></div>";
    if ($result = $mysqli->query("SELECT username, namecolor_fg, namecolor_bg FROM users WHERE id=" . $authorid)) {
        while ($row = $result->fetch_assoc()) {
            $tms = explode(":", $timestamp);
            unset($tms[2]);
            if($edited == 0) {
                $html_message = "<div class='msgln'><span class='chat-time'>" . join(":", $tms) . "</span> <a class='taglink' href='javascript:insert_mention(\"" . $row["username"] . "\");'><b class='user-name' style='color: " . $row["namecolor_fg"] . "; background-color: " . $row["namecolor_bg"] . "'>" . $row["username"] . "</b></a> " . $text . "<br></div>";
            } else {
                $html_message = "<div class='msgln'><span class='chat-time'>" . join(":", $tms) . "</span> <a class='taglink' href='javascript:insert_mention(\"" . $row["username"] . "\");'><b class='user-name' style='color: " . $row["namecolor_fg"] . "; background-color: " . $row["namecolor_bg"] . "'>" . $row["username"] . "</b></a> " . $text . " <span class='edited'>(edited)</span><br></div>";
            }
        }
    }
    return $html_message;
}
?>

javascript（index.php）：

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script>
                function loadLog() {
                    console.log("[DEBUG] Refreshed chat");
                    var oldscrollHeight = $("#chatbox")[0].scrollHeight - 20; //Scroll height before the request
                    $.ajax({
                        url: "refresh.php",
                        cache: false,
                        success: function(html) {
                            $("#chatbox").html(html); //Insert chat log into the #chatbox div
                            //Auto-scroll           
                            var newscrollHeight = $("#chatbox")[0].scrollHeight - 20; //Scroll height after the request
                            if (newscrollHeight > oldscrollHeight) {
                                $("#chatbox").animate({
                                    scrollTop: newscrollHeight
                                }, 'normal'); //Autoscroll to bottom of div
                            }
                        }
                    });
                }
                setInterval(loadLog, 500);
</script>