jquery 进度条 - 一次加载所有内容

我想要一个 jQuery 进度条，它根据服务器端请求的状态进行更新。我的代码基于本教程但它使用文件上传器作为基础（与this问题）。如果没有文件上传器，我无法让它正常工作。问题是进度条仅在 process.php 完成后更新。它不是异步请求进度更新，而是等待整个过程完成。我只看到数据：数据警报一次。

有任何想法吗？

Webpage:

<form id="upload-form" action='process.php' method="post" target="upload-frame">
<input type="hidden" id="uid" name="UPLOAD_IDENTIFIER" value="<?php echo $uid; ?>" >
<input type="submit" value="Submit" />
</form>

<div id="progressbar"></div>

<iframe id="upload-frame" name="upload-frame" style="display:none"></iframe>

Process.php - 提交表单时调用

<?php
session_start();
$varArray=array(1,2,3,4);
$_SESSION['total']=count($varArray);

foreach($varArray as $val){
    $_SESSION['current']=$val;
    sleep(2);
}
?>

javascript

$(document).ready(function() {
    var started = false;// This flag determines if the upload has started
    $(function() {
        // Start progress tracking when the form is submitted
        $('#upload-form').submit(function() {
            $('#progressbar').progressbar();// Initialize the jQuery UI plugin

            // We know the upload is complete when the frame loads
            $('#upload-frame').load(function() {
                // This is to prevent infinite loop
                // in case the upload is too fast
                started = true;
                // Do whatever you want when upload is complete
                alert('Upload Complete!');
            });

            // Start updating progress after a 1 second delay
            setTimeout(function() {
                // We pass the upload identifier to our function
                updateProgress($('#uid').val());
            }, 1000);
        });
    });

    function updateProgress(id) {
        var time = new Date().getTime();
        // Make a GET request to the server
        // Pass our upload identifier as a parameter
        // Also pass current time to prevent caching
        $.ajax({
            url: 'getProgress.php',
            type: "GET",
            cache: false,
            data: {'uid':id}, 
            dataType: 'text',
            success: function(data){
                alert("data: " + data);
                var progress = parseInt(data, 10);
                if (progress < 100 || !started) {
                    // Determine if upload has started
                    started = progress < 100;
                    // If we aren't done or started, update again
                    updateProgress(id);
                }
                // Update the progress bar percentage
                // But only if we have started
                started && $('#progressbar').progressbar('value', progress);
            }
        });
    }
}(jQuery));

getProgress.php - 由 ajax 请求调用：

<?php
session_start();
if (isset($_REQUEST['uid'])) {
    if (isset($_SESSION['total']) && isset($_SESSION['current'])) {
        // Fetch the upload progress data
        $total = $_SESSION['total'];
        $current = $_SESSION['current'];
        // Calculate the current percentage
        $percent_done = round($current/$total*100);
        echo $percent_done;
    }else{
        echo 100;// If there is no data, assume it's done
    }
}
?>

AFAIK，PHP 会话实际上是同步的。这意味着 Process.php 脚本会阻止 getProgress.php 脚本运行，直到 Process.php 完成会话为止。

那么发生的事情是：

1. Process.php启动并调用session_start()
2. 服务器将会话控制权交给session_start()
3. getProcess.php启动并调用session_start()
4. 服务器会阻止 getProcess.php，直到会话不再使用为止。
5. Process.php 完成并关闭会话。
6. 服务器恢复 getProcess.php 并赋予它对会话的控制权。
7. getProcess.php 现在看到该过程已完成。

See http://www.php.net/manual/en/function.session-write-close.php.

会话数据通常在脚本终止后存储，无需调用 session_write_close()，但由于会话数据被锁定以防止并发写入，因此任何时候只有一个脚本可以对会话进行操作。 [...]

我还没有测试以下代码，因为我目前无法访问服务器，但我想类似的东西应该可以工作：

<?php
$varArray=array(1,2,3,4);
session_start();
$_SESSION['total']=count($varArray);
session_write_close ();

foreach($varArray as $val){
    session_start();
    $_SESSION['current']=$val;
    session_write_close ();
    sleep(2);
}
?>