dataurl to image for download in php - php

Question

I'm creating image using canvas and using following script,
function getImage() {
var canvas1 = document.getElementById("images");
if (canvas1.getContext) {
var ctx = canvas1.getContext("2d");
var myImage = canvas1.toDataURL("image/jpg");
}
$('<form action="download.php" method="POST">' +
'<input type="hidden" name="aid" value="' + myImage + '">' +
'</form>').submit();
}
And in my Download.php file is,
<?php $img = $_POST['aid'];
echo "<img src=".$img.">";
?>
it showing image correctly. But i wanna give download button with jpg format or pdf format.
How i can use?
I used base64_decode(); method. But i cant solve.
Help me...

Answer 1

Thanks for all. but I got answer using,
file_put_contents();
But thing, i dont know how to use. Finally i got it from this Answer.
Answer is,
$data = 'data:image/png;base64,AAAFBfj42Pj4';
list($type, $data) = explode(';', $data);
list(, $data) = explode(',', $data);
$data = base64_decode($data);
file_put_contents('/tmp/image.png', $data);
But still i'm waiting for download button with option of image/pdf format.

Answer 2

Try this:
PHP echo'ed image with link
<?php
$img = $_POST['aid'];
echo "";
?>
download_image.php
<?php
$img = "myimage.jpg";
// fix for IE catching or PHP bug issue
header("Pragma: public");
header("Expires: 0"); // set expiration time
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
// browser must download file from server instead of cache
// force download dialog
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
// use the Content-Disposition header to supply a recommended filename and
// force the browser to display the save dialog.
header("Content-Disposition: attachment; filename=".basename($img).";");
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".filesize($img));
readfile("$img");
exit();
?>