AJAX wont call its PHP script while another PHP script is running

问题

Scenario:

I have two PHP scripts to be called simultaneously:

First script will run several minutes (PHP based file download), depending on downloaded file size
Second PHP script is supposed to be called within regular intervals to monitor execution of the first script - file progress download. To avoid opening new windows upon script completion, it is called via AJAX.

Problem:

The regularly called AJAX monitoring script is not processed during the execution of the first long running PHP(later download) script. Only if the first script is finished the AJAX called PHP script gets processed.

I spent many hours over this problem. I have simplified my test scripts as much as possible. However, I still can not get the AJAX script working during execution of the main php script. Neither can I obtain intermediary feedback values from the main-download script, in any other way.

Would you be so kind and analyze my code samples please? They have the precise form as I use them now. If possible, would you be so kind and run them in your environment? I suspect the problem can be in my WAMP environment.

PHP Version 5.4.12
Apache/2.4.4 (Win64) PHP/5.4.12
Windows 7 x64
8GB RAM

Code Samples:

JavaScript code calling both PHP scripts:

<!DOCTYPE html>
<html>
<head>
    <title>Title of the document</title>
</head>

<body onload="callScripts();">


<script type="text/javascript">

    // call both PHP scripts(download and monitoring) in desired order
    callScripts = function()
    {
        // run long running (later Download) PHP script
        console.log("Calling: PHP/fileDownload.php");
        window.location.href = 'PHP/fileDownload.php';

        // call the monitoring PHP script multiple times in 2 second intervals
        window.setTimeout(function(){startDownloadMonitoring()}, 1000);
        window.setTimeout(function(){startDownloadMonitoring()}, 3000);
        window.setTimeout(function(){startDownloadMonitoring()}, 5000);
        window.setTimeout(function(){startDownloadMonitoring()}, 7000);
        window.setTimeout(function(){startDownloadMonitoring()}, 9000);
    };


    // call monitoring PHP script via AJAX
    function startDownloadMonitoring()
    {
        console.log("Calling startDownloadMonitoring()...");

        var xmlhttp;

        if (window.XMLHttpRequest)
        {// code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp=new XMLHttpRequest();
        }
        else
        {// code for IE6, IE5
            xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
        }

        xmlhttp.onreadystatechange = function()
        {
            if (xmlhttp.readyState==4 && xmlhttp.status==200)
            {
                console.log("Response Received: " + xmlhttp.responseText);
            }
        }
        xmlhttp.open("GET", "PHP/fileDownloadStatus.php", true);
        xmlhttp.send();
    }
</script>
</body>
</html>

PHP Monitoring Script(fileDownloadStatus.php)

<?php

include 'ChromePhp.php';

// start session, update session variable, close session
session_start();
$_SESSION['DownloadProgress']++;
ChromePhp::log('$_SESSION[\'DownloadProgress\'] = ' . $_SESSION['DownloadProgress']);
session_write_close();    

echo "success";
?>

PHP long-running script (fileDownload.php)

<?php
include 'ChromePhp.php';

// disable script expiry
set_time_limit(0);

// start session, define variable, close session
session_start();

// prepare session variables
$_SESSION['DownloadProgress'] = 10;

session_write_close();

// execute for 60 seconds    
for( $count = 0; $count < 60; $count++)
{
    sleep(1);
}

?>

回答1:

The first script it's not send through ajax:

 // run long running (later Download) PHP script
  console.log("Calling: PHP/fileDownload.php");
  window.location.href = 'PHP/fileDownload.php';

You simply redirect the user to another page, and because you have download headers in php, the file is downloaded in the same page.

You can easily achieve your scope through an iframe. You set the source of that iframe : 'PHP/fileDownload.php' and then simply call your ajax download checker.

Short example:

<iframe src="PHP/fileDownload.php">

<script>
        window.setTimeout(function(){startDownloadMonitoring()}, 1000);
        window.setTimeout(function(){startDownloadMonitoring()}, 3000);
        window.setTimeout(function(){startDownloadMonitoring()}, 5000);
        window.setTimeout(function(){startDownloadMonitoring()}, 7000);
        window.setTimeout(function(){startDownloadMonitoring()}, 9000);
        // .... blah blah
</script>

回答2:

When you call

    window.location.href = 'PHP/fileDownload.php';

the script execution stops (not immediately, see https://stackoverflow.com/a/2536815/2806497).

Are you sure ajax calls to fileDownloadStatus.php are executed ?

A solution would be to call the fileDownloadStatus.php file by an ajax asynchronous call, or maybe to load it into an iframe you put in your page.

Hope that helps.

来源：https://stackoverflow.com/questions/19683192/ajax-wont-call-its-php-script-while-another-php-script-is-running

标签

javascript

php

ajax

html5

wamp