Scenario:
I have two PHP scripts to be called simultaneously:
- The first script will run several minutes (PHP based file download), depending on downloaded file size. It is placed into
<iframe> so it can run separately and does not block the browser.
- The second PHP script is supposed to be called in 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:
I have placed the long-running PHP Script (download script) into <iframe> so this script can run asynchronously with other monitoring PHP script. However, despite the main script is in <iframe>, when the webpage starts execution, the script starts and blocks execution of the remaining JavaScript code and monitoring script called multiple times via AJAX.
It is important to have the short-running monitoring PHP script called simultaneously with the long-running PHP (download) script, so the short-running (monitoring)script can provide feedback to JavaScript.
Would you be so kind and analyze my code samples please? I have no idea, where is my problem. My code is so simple, that everything should be running well.
- PHP Version 5.4.12
- Apache/2.4.4 (Win64) PHP/5.4.12
- Windows 7 x64
- 8GB RAM
- Google Chrome Version 30.0.1599.101 m
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()
{
// 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>
<iframe src="PHP/fileDownload.php"></iframe>
</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 if session is not already started
session_start();
// prepare session variables
$_SESSION['DownloadProgress'] = 10;
session_write_close();
for( $count = 0; $count < 60; $count++)
{
sleep(1);
print("fileDownload Script was called: ". $count);
echo "Download script: " . $count;
ob_flush();
flush();
}
?>
Screenshot:
PHP Scripts Execution Order - browser waits to finish the script in <iframe>
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