(PHP 5 >= 5.2.0, PHP 7, PECL swoole >= 1.9.0)
swoole_select — Select the file descriptions which are ready to read/write or error in the eventloop
&$read_array
   , array &$write_array
   , array &$error_array
   [, float $timeout
  ] ) : int
read_array
write_array
error_array
timeout