For this script to work, rcon must be enabled on the server, by setting enable-rcon=true in the server's server.properties file. A password must also be set, and provided in the script.

use thedudeguy\Rcon;

$host = 'some.minecraftserver.com'; // Server host name or IP
$port = 25567;                      // Port rcon is listening on
$password = 'server-rcon-password'; // rcon.password setting set in server.properties
$timeout = 3;                       // How long to timeout. Default 3

$rcon = new Rcon($host, $port, $password, $timeout);

if ($rcon->connect())
{
  $rcon->send_command("say Hello World!");
}