PHP没有从ajax调用输出CSV

我有一个按钮，当点击它时，它应该向ajax调用提交变量，然后创建并下载csv，但由于某些原因，文件没有下载。然而，我在Chrome开发工具中得到了正确的输出：

这是我所拥有的：

index.php

<form class="navbar-form navbar-left" method="post">
<input hidden id="ajaxquery" value="<?php echo $ajaxquery;?>">
<button type="button" class="btn btn-success btn-lg" id="downloadcsv">Download CSV</button>
</form>

script.js

$(document).ready(function() {
var csvquery = function(){
    function getUrlParameter(sParam)
{
    var sPageURL = window.location.search.substring(1);
    var sURLVariables = sPageURL.split('&');
    for (var i = 0; i < sURLVariables.length; i++) 
    {
        var sParameterName = sURLVariables[i].split('=');
        if (sParameterName[0] == sParam) 
        {
            return sParameterName[1];
        }
    }
}     
    ajaxquery = $('#ajaxquery').val();
    department = getUrlParameter('department');
    startdate = getUrlParameter('startdate');
    enddate = getUrlParameter('enddate');
    staffsearch = getUrlParameter('staffsearch');
                $.ajax({
                    type: 'POST', // type
                    url: '../report/csv.php', // request file the 'check_email.php'
                    data: {ajaxquery:ajaxquery, department: department, startdate:startdate, enddate: enddate, staffsearch: staffsearch},
                    success: function(responseText) {
    }
                    }); // end success
            }
$('#downloadcsv').click(csvquery);
});

csv.php

session_start();
require '../connect.php';
header('Content-Type: text/csv; charset=utf-8');
header('Content-Disposition: attachment; filename=data.csv');
$output = fopen('php://output', 'w');
fputcsv($output, array('Name', 'Department','Hours Worked', 'On Holiday', 'Ill' , 'Date'));
$sql = "SELECT time.id as timeid, time.staff_id, time.timein, time.onholiday, time.dateadded, time.ill, time.notes, staff.id AS staffid, department.id AS departmentid, department.department_name, staff.staff_name, staff.department_id FROM time, staff, department WHERE staff.id = time.staff_id AND staff.department_id = department.id ORDER BY `time`.`dateadded` ASC ;";
$rows = mysqli_query($connect, $sql);
while ($rowcsv = mysqli_fetch_assoc($rows)){ 
    fputcsv($output, array($rowcsv['staff_name'],$rowcsv['department_name'],$rowcsv['timein'],$rowcsv['onholiday'],$rowcsv['ill'],$rowcsv['dateadded']));
};
readfile("php://output");