(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)
socket_set_nonblock — Sets nonblocking mode for file descriptor fd
The socket_set_nonblock() function sets the
O_NONBLOCK flag on the socket specified by
the socket parameter.
When an operation (e.g. receive, send, connect, accept, ...) is performed on a non-blocking socket, the script will not pause its execution until it receives a signal or it can perform the operation. Rather, if the operation would result in a block, the called function will fail.
Example #1 socket_set_nonblock() example
<?php
$socket = socket_create_listen(1223);
socket_set_nonblock($socket);
socket_accept($socket);
?>
This example creates a listening socket on all interfaces on port 1223 and
sets the socket to O_NONBLOCK mode.
socket_accept() will immediately fail unless there is a
pending connection exactly at this moment.
Beware, when using this function within a loop (i.e. a demon with a socket). The socket_accept(), for example, emits a warning each time there is no incoming connection available to be read. My php error log file got huge in a matter of seconds, eventually crashing the server.
Of course, i used the @ before the function to take care of that problem.
[EDITOR: One can (and should) use socket_select to detect a new connection on a socket (it's a "readable" event)]