Basic post handler as a HTTP response code example.

html_responses.php

<?php
$status = 500; // if we don't change this then the problem is this code
$result = array();

if (empty($_FILES['file']['tmp_name'])) {
    $status = 400;
    $result['message'] = 'No file found.';
} else if (empty($_FILES['file']['name'])) {
    $status = 400;
    $result['message'] = 'No file name found.';
} else if (!file_exists($_FILES['file']['tmp_name'])) {
    $status = 400;
    $result['message'] = 'File not found.';
} else {
    $extension = pathinfo($_FILES['file']['name'], PATHINFO_EXTENSION);
    if (!in_array($extension, array('jpeg', 'jpg')) {
        $status = 415;
        $result['message'] = 'Unsupported file type.';
    }
    else if (empty($_REQUEST['uid'])) {
        $status = 400;
        $result['message'] = 'Missing unique ID';
    } else {
            $filesFolder = DIR_BASE.'/files/uploads/images';
            if (!is_dir($filesFolder)) {
                mkdir($filesFolder, 0777, true);
            }
            if (!is_dir($filesFolder)) {
                $status = 500;
                $result['message'] = 'Unable to create directory';
            } else {
                if (!move_uploaded_file($_FILES['file']['tmp_name'], $filesFolder.'/'.$_FILES['file']['name'])) {
                    $status = 500;
                    $result['message'] = 'Unable to move file into place.';
                } else {
                    // Success!
                    $status = 200;
                    $result['name'] = $_FILES['file']['name'];
                }
            }
        }
    }
}

http_response_code($status);
echo json_encode($result);