PHP Socket客户端：测试服务器连接

Question

I have socket client which connects to server and which wait for datas to be sent by this server. It works fine but, when server has a disconnection, it has to be detected by socket client in order to try a reconnection.

Client socket code :

$co = false;
while (!$co) {

    $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
    if ($socket === false) {
        echo "socket_create()error :  " . socket_strerror(socket_last_error()) . "
";
    } else {
        echo "OK 1.
";
    }

    echo "Try connection '$address' on port '$service_port'... 
";
    $result = socket_connect($socket, $address, $service_port);
    if ($socket === false) {
        echo "socket_connect() error : ($result) " . socket_strerror(socket_last_error($socket)) . "
";
    } else {
        socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array("sec" => 1, "usec" => 0));
        echo "OK 2.
";
        $co = true;
    }
}

while (true) {
    echo 'read' . PHP_EOL;
    socket_clear_error($socket);
    $out = socket_read($socket, 2048);
    $socket_last_error = socket_last_error($socket);
    $strErr = socket_strerror($socket_last_error) . ' ' . $socket_last_error;
    echo("socket_last_error : " . $strErr);
    var_dump($out);
} 

Problem is when client socket is correctly connected to server, there's socket_last_error with value 'Resource temporarily unavailable 11' and 'socket_read' function return false when server doesn't send data.

But when server is deconnected, there's socket_last_error with value 'Success 0' and 'read' function return ''

PHP doc says :

socket_read() returns data as string on success, or FALSE on error (including case where remote host has closed connection).

So functions results are unexpected and I would like to know what's the right method to detect a server disconnection in order to try a new connection?

Thanks in advance for your answers.