PHP Polling Sockets Eats Up CPU - php

Question

I've written a pair of PHP socket servers that listen around for commands and respond to them. The problem is that they do so by listening in an infinite loop, and thus are eating up CPU.
So how do I do this (1) without eating up CPU; and (2) without slowing down the socket commands, particularly if I have several come in in sequence?
$sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1);
socket_bind($sock, $address, $port);
socket_listen($sock);
$clients = array($sock);
$write = NULL;
$except = NULL;
while (true) {
$read = $clients;
if (socket_select($read, $write, $except, 0) < 1)
continue;
if (in_array($sock, $read)) {
$clients[] = socket_accept($sock);
$key = array_search($sock, $read);
unset($read[$key]);
}
foreach ($read as $read_sock) {
/* I tried putting a tiny sleep here, but if I run several socket connections for the same user sequentially, they see a notable slowdown */
$data = #socket_read($read_sock, 1024, PHP_NORMAL_READ);
if ($data === false) {
$key = array_search($read_sock, $clients);
unset($clients[$key]);
echo "client disconnected.\n";
continue;
}
$data = trim($data);
/* And this is the heart of my loop */
}
} // end of reading foreach
}
// close the listening socket
socket_close($sock);