ajax post then get file to use - php

Question

I am new on php, and I am writing a code which allows me to send some data to php then doing some exec(), and then get the process output back to use(e.g. post one web page).
$.ajax({
url: 'some.php',
type: 'POST',
data: someData,
async: false,
success: function (html) {
$('#showonscreen').html(html);
},
cache: false,
contentType: false,
processData: false
});
and on php part is like
<?php
/*something like $cmd here*/
exec("$cmd $target_file $Output_fileName $upper $lower");
echo "<br/>done";
?>
after that exec() generates a output file (e.g image)with that Output_fileName under the root folder.
My question is can I get(or load?) this file directly back client side to use?(in success part?) Or I need a $.get to request from server again to get that file?
So, on client side, it works like, they upload a image, then click button to process it, then the result image is store under server root, then grab from it to show on the web page.
any help

Answer 1

On Server Side
First its good if you capture o/p like below
exec('your_command 2>&1', $outputAndErrors, $return_value);
Then
if (!$return_value) {
// Ok lets decide what next
} else {
// Ooops some problem error handling
}
As you mentioned if you are dealing with image then
echo base64_encode(file_get_contents($your_file_generated));
for plain text you can just
header('Content-type: text/plain; charset=utf-8');
echo file_get_contents($your_file_generated);
// OR
echo readfile($your_file_generated);
On Client Side
$.ajax({
..
..
success: function (server_response) {
$('#showonscreen').html('<img src="data:image/png;base64,'+ server_response +'"/>');
},
..
..
});