public function __construct()
{
// build the chain of responsibility
$l = new DebugLogger(Logger::DEBUG);
$e = new EmailLogger(Logger::NOTICE);
$s = new StderrLogger(Logger::ERR);
$l->setNext($e->setNext($s));
$l->message("Entering function y.", Logger::DEBUG);
// handled by DebugLogger
$l->message("Step1 completed.", Logger::NOTICE);
// handled by DebugLogger and EmailLogger
$l->message("An error has occurred.", Logger::ERR);
// handled by all three Loggers
}
