src/Binary/Request/StandardBinaryRequest.php
public function onNotification($notification_code, $severity, $message, $message_code, $bytes_transferred, $bytes_max)
    {
        switch($notification_code) {
            case STREAM_NOTIFY_PROGRESS:
                $this->emit('progress', [$bytes_transferred]);
                break;
            case STREAM_NOTIFY_FILE_SIZE_IS:
                $this->emit('request.start', [$this->url, $bytes_max]);
                break;
        }
    }
public function onNotification($notification_code, $severity, $message, $message_code, $bytes_transferred, $bytes_max)
    {
        switch($notification_code) {
            case STREAM_NOTIFY_PROGRESS:
                $this->emit('progress', [$bytes_transferred]);
                break;
            case STREAM_NOTIFY_FILE_SIZE_IS:
                $this->emit('request.start', [$this->url, $bytes_max]);
                break;
        }
    }
Callback used when progress is made requesting.

@param $notification_code
@param $severity
@param $message
@param $message_code
@param $bytes_transferred
@param $bytes_max
@return void