cURL php download and upload without save in the middle
$ch = curl_init();
curl_set_opt($ch, CURLOPT_HEADERFUNCTION, 'read_header');
curl_set_opt($ch, CURLOPT_WRITEFUNCTION, 'read_body');

function read_header($ch, $data) {
    // Ok, so the header is going to come in here.
    // I assume you will need data, such as MIME type and what not.
    print_r($data);
    return strlen($data); //This means that we handled it, so cURL will keep processing
}

function read_body($ch, $data) {
    // This is where the body of the content will be, in chunks.
    // This function will be called multiple times.
    print_r($data);
    return strlen($data); //Again, if we don't do this, cURL will cancel.
}