Logger allowing either log by selected logger or to stack loggers and log to each of them.
Originally comes from http://addons.nette.org/cs/logger by Jan Smitka and Martin Pecka
$fileLogger = new FileLogger();
$outputLogger = new OutputLogger();
$stack = new Stack(array(
'loggers' => array($fileLogger, $outputLogger)
));
$stack->logMessage('Just a casual informational message');
$stack->logMessage(ILogger::ALERT, 'Alert, CPU load exceeded %d %%', 300);