File upload process not working on live server

Hi,

I have integrate the PHP api of dropbox on localhost. It is working fine. But when host on live server , file upload process not working. download process working fine.

Please help regarding this.

I have use these code in index.php

require 'app/start.php';
require 'app/dropbox_auth.php';
var_dump($client->getAccountInfo());
echo "Test";

echo "</br>";
//-------for download start----
$client->getFile('/select.html',fopen('files/select.html','wb'));

//-------for download end----


//-------for upload start----
        $file = fopen('/files/Koala.jpg','rb');
    $size = filesize('/files/Koala.jpg');
    $client->uploadFile('/Koala.jpg',Dropbox\Writemode::add(),$file,$size);