public function header($key, $value = null)
	{
		if( is_null($value) )
		{
			$pos = strpos($key, ":");
			if( ! $pos )
			{
				return $this;
			}

			$value = substr($key, $pos + 1);
			$key = substr($key, 0, $pos);
		}
		$this->headers->set($key, $value);
		return $this;
	}