To expand a bit more on what "tim at e2-media dot co dot nz" started.
SO_SNDTIMEO is one of the many constants you can use with socket_set_option.
See http://ca.php.net/manual/en/ref.sockets.php for the available Predefind Constants and visit http://man.he.net/man2/setsockopt for the meaning of the ones relevant.
Tim's example might seem at first a bit non-intuitive since he is using the SO_SNDTIMEO constant. Which means, if the socket has to send out data, it must do it within the limit specified - in his case 10 seconds. Usually you won't set a timeout for sending out data. Nevertheless, the example is valid, and there are situations where you need to do so.
A more intuitive use of socket_set_option would be to set a time out for a blocking socket (a socket that waits for data to be receive when read from). You would do this like so:
socket_set_option($socket,SOL_SOCKET, SO_RCVTIMEO, array("sec"=>0, "usec"=>100));
Notice that sec= 0 and usec= 100; Depending on how long you want your program to wait to recieve data, you might want to change these values.