如何防止脚本导致 PHP 的无限加载时间

我一直在寻找一种方法将变量id从索引.php转移到（除其他外）更新检查.php。最初，这导致了无休止的加载时间——即页面在本地主机上永远等待。我将其缩小为导致此错误的session_start();。如果我删除session_start();并用实际的 id 变量（如 'stories/film.txt';）替换'stories/'. $_SESSION['id'] .'.txt';，加载没有任何问题——除了我需要该变量的事实。

我还注意到我有时会在控制台中Failed to load resource: net::ERR_CACHE_MISS。

我试图修补并找到发生这种情况的原因以及如何解决它，但我的大脑很痛，我希望在这种情况下有更多经验的人能够在这种错误搜索中提供一些帮助（值得一提的是，我不习惯使用 PHP 或后端， 来自前端作为设计师）。

编辑 – 所以问题不在于 PHP，而在于这个脚本是否可以在保持功能的同时调整此脚本以使其发挥良好作用？

/**
 * AJAX long-polling
 *
 * 1. sends a request to the server (without a timestamp parameter)
 * 2. waits for an answer from server.php (which can take forever)
 * 3. if server.php responds (whenever), put data_from_file into #response
 * 4. and call the function again
 *
 * @param timestamp
 */
function getContent(timestamp)
{
    var queryString = {'timestamp' : timestamp};
    $.ajax(
        {
        type: 'GET',
        url: 'update-check.php',
        data: queryString,
        success: function(data){
            // put result data into "obj"
            var obj = jQuery.parseJSON(data);
            // put the data_from_file into #response
            $('#response').html(obj.data_from_file);
            // call the function again, this time with the timestamp we just got from server.php
            getContent(obj.timestamp);
                //timeout to avoid endless loading? didn't make a difference
                timeout: 3000 // sets timeout to 3 seconds
            }
        }
    );
}
// initialize jQuery
$(function() {
    getContent();
});

更新检查.php

<?php
session_start();

/**
 * Server-side file.
 * This file is an infinitive loop. Seriously.
 * It gets the file data.txt's last-changed timestamp, checks if this is larger than the timestamp of the
 * AJAX-submitted timestamp (time of last ajax request), and if so, it sends back a JSON with the data from
 * data.txt (and a timestamp). If not, it waits for one seconds and then start the next while step.
 *
 * Note: This returns a JSON, containing the content of data.txt and the timestamp of the last data.txt change.
 * This timestamp is used by the client's JavaScript for the next request, so THIS server-side script here only
 * serves new content after the last file change. Sounds weird, but try it out, you'll get into it really fast!
 */
// set php runtime to unlimited
set_time_limit(0);
/* $data_source_file = 'stories/film.txt'; */
$data_source_file = 'stories/'. $_SESSION['id'] .'.txt';
// main loop
while (true) {
    // if ajax request has send a timestamp, then $last_ajax_call = timestamp, else $last_ajax_call = null
    $last_ajax_call = isset($_GET['timestamp']) ? (int)$_GET['timestamp'] : null;
    // PHP caches file data, like requesting the size of a file, by default. clearstatcache() clears that cache
    clearstatcache();
    // get timestamp of when file has been changed the last time
    $last_change_in_data_file = filemtime($data_source_file);
    // if no timestamp delivered via ajax or data.txt has been changed SINCE last ajax timestamp
    if ($last_ajax_call == null || $last_change_in_data_file > $last_ajax_call) {
        // get content of data.txt
        $data = file_get_contents($data_source_file);
        // put data.txt's content and timestamp of last data.txt change into array
        $result = array(
            'data_from_file' => $data,
            'timestamp' => $last_change_in_data_file
        );
        // encode to JSON, render the result (for AJAX)
        $json = json_encode($result);
        echo $json;
        // leave this loop step
        break;
    } else {
        // wait for 1 sec (not very sexy as this blocks the PHP/Apache process, but that's how it goes)
        sleep( 1 );
        continue;
    }
}