how to filter inside php socket

i have this socket writed on php, the problem is:

how to filter users and send a msg to choosed user,

example: from a external form i can choose an user and send a msg, but i need the msg just go to a selected user, no to all connected users, because sometimes i send a function to move user and all user is moved because all users receive the function and not just the choosed user,

how i can filter by user and the function send to a selected user?

the function is just a javascript line (but how i can do that? with a if or else??? )

//
//error_reporting(1);
set_time_limit(0);
//
//
define('CON_IP', '127.0.0.1');
define('CON_PORT', 4000);
//
//
//INICIO KEEP ALIVE
$KTimer   = (20);
$LastTime = time();
//END KEEP ALIVE
//
$null     = NULL; //null var
//
$socket   = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); // CREAR STREAM SOCKET TCP
socket_set_option($socket, SOL_SOCKET, SO_REUSEADDR, 1); //REUTILIZAR PUERTO
socket_bind($socket, CON_IP, CON_PORT); //VINCULA EL SOCKET AL HOST ESPECIFICADO
socket_listen($socket); //ESCUCHAR PUERTO
//
//CREAR Y AÑADIR SOCKETS A LA LISTA
$clients = array(
    $socket
);
echo ('running...');
//
//INICIAR CICLO PARA QUE EL SCRIPT NO SE DETENGA
//
while (true) {
    //
    //MANEJAR MULTIPLES CONEXIONES
    $changed = $clients;
    //RETORNA LOS RECURSOS DE SOCKET EN EL ARRAY ($changed)
    socket_select($changed, $null, $null, 0, 10);
    //
    //BUSCA UN NUEVO SOCKET
    if (in_array($socket, $changed)) {
        $socket_new = socket_accept($socket); //ACEPTAR NUEVO SOCKET
        $clients[]  = $socket_new; //AÑADIR SOCKET CLIENTE A ARRAY()
        //
        $header     = socket_read($socket_new, 1024); //LEER DATOS ENVIADOS POR EL SOCKET
        //
        //HEADER FIX
        if (substr($header, 0, 3) == 'GET' || substr($header, 0, 4) == 'POST' || substr($header, 0, 4) == 'OPTI') {
            //
            //HTML HEADER INCLUDE
            socket_write($socket_new, ("HTTP/1.1 200 OK\r\n"));
            socket_write($socket_new, ("Server: NStream/5.8.425.10413\r\n"));
            socket_write($socket_new, ("Content-Type: text/html; charset=utf-8;\r\n"));
            socket_write($socket_new, ("Cache-Control: private\r\n\r\n"));
            //
            //
            socket_write($socket_new, $html);
        }
        //END HEADER FIX
        //
        socket_getpeername($socket_new, $RemoteAddr, $RemotePort); //OBTENER DIRECCION IP Y PUERTO DE LOS SOCKETS CONECTADOS
        MsgSend('[' . $RemoteAddr . ':' . $RemotePort . ']=>>IC', 'ILC'); //NOTIFICAR NUEVAS CONEXIONES
        //
        //CREAR UN NUEVO CANAL PARA SOCKETS NUEVOS
        $found_socket = array_search($socket, $changed);
        unset($changed[$found_socket]);
        //CMD PARSE
        //si sesion coincide con usuario, mostrar packet
        if (!empty($header)) {
            $GedCmdId = (explode(':', @explode('"', $header)[1]));
            //CMD SY
            if ($GedCmdId[0] == 'sy') {
                $ParsePaket = (explode('|', preg_replace(array(
                    "/'/",
                    "/,/"
                ), array(
                    NULL,
                    '|'
                ), $GedCmdId[1])));
                $header     = ("parent.ParsePacket(\"sy:'" . $ParsePaket[0] . "','" . $ParsePaket[1] . "','" . $ParsePaket[2] . "','" . $ParsePaket[3] . "','" . $ParsePaket[4] . "','" . $ParsePaket[5] . "'," . $ParsePaket[6] . "\");");
            }
        }
        //}
        //END CMD PARSE
    }
    //VOID
    //
    //KA - FIX
    if (time() - $LastTime > $KTimer) {
        MsgSend('[' . $LastTime . '==>' . time() . ']=>>KA(' . (time() - $LastTime) . ')', 'ILC');
        MsgSend("k();");
        $LastTime = time();
        continue 1;
    }
    //END KA - FIX
    //
    //LOOP A TRAVEZ DE TODOS LOS SOCKETS CONECTADOS
    foreach ($changed as $changed_socket) {
        //check for any incomming data
        if (!empty($header)) {
            //PREPARAR INFO PARA SER ENVIADA A SOCKET
            //prepare data to be sent to client
            MsgSend('[' . $RemoteAddr . ':' . $RemotePort . ']=>>MSG', 'ILC');
            MsgSend($header); //send data
        }
        $buf = @socket_read($changed_socket, 1024, PHP_NORMAL_READ);
        if ($buf === false) { // VERIFICAR CLIENTES DESCONECTADOS
            //
            // REMOVER CLIENTE DE ARRAY ($clients)
            $found_socket = array_search($changed_socket, $clients);
            socket_getpeername($changed_socket, $RemoteAddr);
            unset($clients[$found_socket]); //NOTIFICAR NUEVAS DESCONEXIONES
            MsgSend('[' . $RemoteAddr . ':' . $RemotePort . ']<<=ID', 'ILC');
        }
    }
}
//
//CIERRA LA ESCUCHA EN EL SOCKET
socket_close($socket);
function MsgSend($msg, $msgt = 'sock')
{
    global $clients;
    if ($msgt == 'ILC') {
        echo ($msg . "\r\n");
    } else {
        if (!empty($msg)) {
            foreach ($clients as $changed_socket) {
                @socket_write($changed_socket, '<script>' . $msg . "</script>\r\n");
            }
        }
    }
    return true;
}