I want to download text file generated in a textarea

here my download.php file code structure goes :

<?php

if(empty($_POST['filename']) || empty($_POST['content'])){
exit;
}

$filename = preg_replace('/[^a-z0-9\-\_\.]/i','',$_POST['filename']);

header("Cache-Control: ");
header("Content-type: text/plain");
header('Content-Disposition: attachment; filename="'.$filename.'"');

echo $_POST['content'];

?>


and the javascript used


(function($){

$.generateFile = function(options){

options = options || {};

if(!options.script || !options.filename || !options.content){
throw new Error("Please enter all the required config options!");
}

var iframe = $('<iframe>',{
width:1,
height:1,
frameborder:0,
css:{
display:'none'
}
}).appendTo('body');


and the script.js

$(document).ready(function(){

$('#download').click(function(e){

$.generateFile({
filename : 'export.txt',
content : $('textarea').val(),
script : 'download.php'
});

e.preventDefault();
});


by these assets i created a web page consisting a TEXTAREA , by entering some text on the textarea and clicking on the download button , a text files is generated and downloaded on the user's system, I packed the source code as a CRX file to use it as a CHROME extension, but while using the extension,the files are'nt generated, while the webpage works absolutely fine !!!