PHP socket server takes a lot of CPU usage - php

Question

I follow some tutorial (1), (2) on internet to create a PHP socket server, and it works quite well. There is only thing is my PHP script takes a lot of CPU usage (99%).
I do not show code here, because my code is similar to the above tutorials.
The main action is written in an infinitive loop
while (true)
{
$this->selectChangedSockets();
$this->handleNewClients();
$this->receiveInput();
$this->checkDisconnections();
}
The functions inside the my loop are just to handle inputs (new client's connection, client's message, etc.), and handle outputs (send back to the client's message, etc.)
My php script is always on top in CPU usage (99%). I read this, and they suggest to put "sleep(1)" in the loop. My socket server is for the real time applications, and I am not sure this is a good way to go?
Anyone who has experience with php socket can give me any suggestion?
Is there any standard php socket server library?
or do I need to run the script in the background?
Updated
Because you mention the function socket_select may pause a little bit, I give you my code:
private function selectChangedSockets()
{
// Reset array of changed sockets
$this->changed = array_merge(array($this->socket), $this->clients);
$null = null;
$res = socket_select($this->changed, $null, $null, 0);
if (false === $res)
{
echo "socket_select() failed, reason: " .
socket_strerror(socket_last_error()) . "\n";
}
}
public function run()
{
while (true) {
$this->selectChangedSockets();
//$this->handleNewClients();
//$this->receiveInput();
//$this->checkDisconnections();
}
}
My PHP script still takes 99% CPU usage.

Answer 1

Your selectChangedSockets method should be blocking, meaning, not return until there are changes on the sockets. See socket_select.
A while ( true ) {} will use 100% CPU time. You will need some kind of delay.
Since you can use socket_select, you can specify a timeout there, using 0% CPU time until there is actually some work to be done:
function selectChangedSockets() {
$read = array($socket1, $socket2); // array of your sockets
$write = NULL;
$except = NULL;
$num_changed_sockets = socket_select($read, $write, $except, NULL);
}
This will wait until one of the sockets in $read has data available. For a server socket, this happens when a new connection is established by a client. For a connected socket, this happens when the client has sent data.
Again, see socket_select for details and examples. Especially the first user contributed note, which uses a while (true), handles new connections, and reads data from clients.
Note however, from the socket_select page, about the 4th parameter:
tv_sec may be zero , causing socket_select() to return immediately. This is useful for polling. If tv_sec is NULL (no timeout), socket_select() can block indefinitely.

Answer 2

My solution is:
if socket server idle 5 second (not receive data), idle mode, relaxes CPU,
<?php
if (!($sock = socket_create(AF_INET, SOCK_DGRAM, 0))) {
$errorcode = socket_last_error();
$errormsg = socket_strerror($errorcode);
die("Couldn't create socket: [$errorcode] $errormsg \n");
}
$server_idle=time();
while (1) {
$buf="";
$r = socket_recvfrom($sock, $buf, 512, MSG_DONTWAIT, $remote_ip, $remote_port);
if ($buf) {
$server_idle=time();
//socket process codes
//.
//.
}
if (time()-$server_idle>5) { // if Server idle 5 second; IDLE Mode!
usleep(100); // IDLE Mode
} else {
// usleep(1); // No IDLE Mode usleep(1) milisecond less CPU process
}
}
?>