View file It's Me/main-file/php/upload.php

<?php
require('../assets/external/Simple-Ajax-Uploader/extras/Uploader.php');

$upload_dir = 'uploads';
$valid_extensions = array('pdf');

$Upload = new FileUpload('fileatt');
$result = $Upload->handleUpload($upload_dir, $valid_extensions);

if (!$result) {
    echo json_encode(array('success' => false, 'msg' => $Upload->getErrorMsg()));   
} else {
    echo json_encode(array('success' => true, 'file' => $Upload->getFileName()));
}