PHP Manual: Shuts down a socket for receiving, sending, or both

bool socket_shutdown ( resource $socket [, int $how = 2 ] )

The socket_shutdown function allows you to stop incoming, outgoing or all data (the default) from being sent through the socket

socket

A valid socket resource created with socket_create.

how

The value of how can be one of the following:

possible values for *`how`*
0	Shutdown socket reading
1	Shutdown socket writing
2	Shutdown socket reading and writing

Returns TRUE on success or FALSE on failure.