PHP マニュアル: Sets socket options

public static bool EventUtil::setSocketOption(
     mixed $socket ,
     int $level ,
     int $optname ,
     mixed $optval
)

Sets socket options.

socket: Socket resource, stream, or numeric file descriptor associated with the socket.
level: One of EventUtil::SOL_* constants. Specifies the protocol level at which the option resides. For example, to retrieve options at the socket level, a level parameter of EventUtil::SOL_SOCKET would be used. Other levels, such as TCP, can be used by specifying the protocol number of that level. Protocol numbers can be found by using the getprotobyname function. See EventUtil constants .
optname: Option name(type). Has the same meaning as corresponding parameter of socket_get_option function. See EventUtil constants .
optval: Accepts the same values as optval parameter of the socket_get_option function.

成功した場合に true を、失敗した場合に false を返します。