PHP detecting TCP client disconnect - php

Question

I got a TCP server up and running, which supports many client connections at the same time, together with reading and sending data. However, when client closes the connection, there is a delay on the server to detect a disconnected client.
// TCP socket created here
$clients = array($socket);
while (true) {
$read = $clients; // Copy of $clients
$write = NULL;
$except = NULL;
$num_changed_sockets = socket_select($read, $write, $except, NULL);
if ($num_changed_sockets === false) {
// ...
} else if ($num_changed_sockets > 0) { // Something changed
printb("In here."); // EDIT
if (in_array($socket, $read)) { // For new connections and removing host from the $clients copy
$newsock = socket_accept($socket);
if ($newsock !== false) {
printb("Client $newsock connected");
$clients[] = $newsock;
}
$key = array_search($socket, $read);
unset($read[$key]);
}
foreach ($read as $read_socket) { // The actual problem starts here?
printb("Read part."); // EDIT
$data = socket_read($read_socket, 128);
if ($data === false) {
printb("Client $read_socket disconnected");
$key = array_search($read_socket, $clients);
socket_close($clients[$key]);
unset($clients[$key]);
continue;
}
}
}
EDIT I:
I just added debug prints in the code. When a single client disconnects, server falls into infinite loop from $num_changed_sockets. Is there way to fix it?
EDIT II:
var_dump gives empty string after a client has disconnected.
EDIT III:
According to last edit, disconnecting the client, if socket_read returns an empty string seems to work. I Found a note from PHP's website:
Note: socket_read() returns a zero length string ("") when there is no more data to read.
Should not this return false, when client disconnects?