(PECL event >= 1.2.6-beta)
EventBuffer::drain — Removes specified number of bytes from the front of the buffer without copying it anywhere
$len
   
   )Behaves as EventBuffer::read() , except that it does not copy the data: it just removes it from the front of the buffer.
len
    The number of bytes to remove from the buffer.
   Returns TRUE on success. Otherwise FALSE.