Download a file built in PHP output buffer from AJAX call

I am trying to build a CSV file in PHP, then call the PHP file from an AJAX call, which will then initiate a download of the CSV file upon success of the AJAX call. This works fine if I save a physical copy of the .csv on the server, but I would like to use php://ouput so I do not have to worry about physical files clogging up the server. Is it possible to initiate a download from returning php://output to AJAX? Here is my code:

HTML/jquery:

<!DOCTYPE html>

<html lang="en">
    <head>
        <meta charset="utf-8" />
        <script type="text/javascript" language="javascript" src="jquery.js"></script>
        <script type="text/javascript">
             $("#download").live("click", function() {
                var request = $.ajax({
                    dataType: 'html',
                    url: 'php.php',
                    success: function(response) {
                        alert('Finished');
                    }
                })
            })
        </script>
    </head>
    <body>
        <h1 id="download">DOWNLOAD</h1>
    </body>
</html>

PHP:

<?php 
    header('Content-type: application/vnd.ms-excel');
    header('Content-disposition: attachment; filename="test.csv"');
    $f = fopen('php://output', 'w');
    fwrite($f,'this,is,a,test');
    fclose($f);
    readfile('php://output');
    return;
?>

I am not sure how to get this to return a File Save dialog from my AJAX call.

This has to be simple, but I can't seem to find any examples that combines these two issues.

You can do this by creating and sending form via jquery (page not reloaded):

$(document).on('click', '#download', function () {
    var form = $(document.createElement('form'));
    form.attr('action', 'php.php');
    form.attr('method', 'GET');
    form.appendTo(document.body);
    form.submit();
    form.remove();
});

Also you can pass post parameters if need:

$(document).on('click', '#download', function () {
    var form = $(document.createElement('form'));
    form.attr('action', 'php.php');
    form.attr('method', 'POST');
    var input = $('<input>').attr('type', 'hidden').attr('name', 'x').val('x value');
    form.append(input);
    form.appendTo(document.body);
    form.submit();
    form.remove();
});

The following works, but is highly inneficient as it calls the php.php file twice. Does anybody have any better ideas?

<!DOCTYPE html>

<html lang="en">
    <head>
        <meta charset="utf-8" />
        <script type="text/javascript" language="javascript" src="jquery.js"></script>
        <script type="text/javascript">
             $("#download").live("click", function() {
                var request = $.ajax({
                    dataType: 'html',
                    url: 'php.php',
                    success: function(response) {
                        window.open('php.php');
                    }
                })
            })
        </script>
    </head>
    <body>
        <h1 id="download">DOWNLOAD</h1>
    </body>
</html>

Is there anyway to cache 'php.php' for just this instance so that it loads instantly under window.open('php.php'), but will reload contents when I click download next?

Why does window.open(response) not work the same?

look this：

if (!headers_sent()) {
    // seconds, minutes, hours, days
    $expires = 60*60*24*14;
    header('Pragma: public');
    header('Cache-Control: maxage=' . $expires);
    header('Expires: ' . gmdate('D, d M Y H:i:s', time() + $expires) . ' GMT');
}

Note: this will not work with POST requests, just GET.

To allow for a file download, you can simply call the below code (say on a button's onclick):