Explain basic PHP Socket server code - php

Question

I'm trying to learn how to make a chat with a socket server.
I noticed everybody uses the same code (ripoff from the zend developer zone).
The problem is no one really explains how it works. Especially the cryptic code after while(true) { .
This would benefit many so i hope someone could take the time and explain the code in detail (DETAIL!).
You can find the code here

Answer 1

I'll answer it myselfe. I went over it line by line.. this is how it works (I'm only explaining the part in the while(true) loops.
1.
// Setup clients listen socket for reading
$read[0] = $sock;
for ($i = 0; $i < $max_clients; $i++) {
if (isset($client[$i]['sock']))
$read[$i + 1] = $client[$i]['sock'];
}
This asings freshly created connections to the $read array to be watched for incoming data.
// Set up a blocking call to socket_select()
if (socket_select($read, $write = NULL, $except = NULL, $tv_sec = 5) < 1)
continue;
Watches the $read array for new data (I'm still a bit unclear how this works)
/* if a new connection is being made add it to the client array */
if (in_array($sock, $read)) {
for ($i = 0; $i < $max_clients; $i++) {
if (empty($client[$i]['sock'])) {
$client[$i]['sock'] = socket_accept($sock);
echo "New client connected $i\r\n";
break;
}
elseif ($i == $max_clients - 1)
echo "Too many clients...\r\n";
}
}
Determines when a new connection is being made, than finds an empty spot in the $client array and add the socket.
This next part I'll split up for easier explanation.
for ($i = 0; $i < $max_clients; $i++) { // for each client
if (isset($client[$i]['sock'])) {
Loops through all the $client array but only works on the ones that actually have a connection.
if (in_array($client[$i]['sock'], $read)) {
$input = socket_read($client[$i]['sock'], 1024);
if ($input == null) {
echo "Client disconnecting $i\r\n";
// Zero length string meaning disconnected
unset($client[$i]);
} else {
echo "New input received $i\r\n";
// send it to the other clients
for ($j = 0; $j < $max_clients; $j++) {
if (isset($client[$j]['sock']) && $j != $i) {
echo "Writing '$input' to client $j\r\n";
socket_write($client[$j]['sock'], $input, strlen($input));
}
}
if ($input == 'exit') {
// requested disconnect
socket_close($client[$i]['sock']);
}
}
} else {
echo "Client disconnected $i\r\n";
// Close the socket
socket_close($client[$i]['sock']);
unset($client[$i]);
}
First it sees if there is still an active connection, if not it closes it.
If there is a connection it read the data, if there is noone this is code for a disconnect.
If there is data it passes it along to other clients (but itselfe).
That's ti. Hope I got it right.

Answer 2

PHP is not multithreaded, because of that you cant build good socket server.
Use Python instead.
http://docs.python.org/library/socketserver.html
http://www.rohitab.com/discuss/index.php?showtopic=24808