Download file through an ajax call php

I have a button and `onclick` it will call an ajax function. Here is my ajax function ``` function csv(){ ajaxRequest = ajax();//ajax() is function that has all the XML HTTP Requests postdata = "data=" + document.getElementById("id").value; ajaxRequest.onreadystatechange = function(){ var ajaxDisplay = document.getElementById('ajaxDiv'); if(ajaxRequest.readyState == 4 && ajaxRequest.status==200){ ajaxDisplay.innerHTML = ajaxRequest.responseText; } } ajaxRequest.open("POST","csv.php",false); ajaxRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded'); ajaxRequest.send(postdata); } ``` I create the csv file based on the user input. After it's created I want it to prompt download or force download(preferably force). I am using the following script at the end of the php file to download the file. If I run this script in a separate file it works fine. ``` $fileName = 'file.csv'; $downloadFileName = 'newfile.csv'; if (file_exists($fileName)) { header('Content-Description: File Transfer'); header('Content-Type: text/csv'); header('Content-Disposition: attachment; filename='.$downloadFileName); ob_clean(); flush(); readfile($fileName); exit; } echo "done"; ``` But If I run it at the end of csv.php it outputs the contents of the file.csv into the page(into the ajaxDiv) instead of downloading. Is there a way to force download the file at the end of csv.php?