A Slim application provides a log object that writes data to a specific output. The actual writing of data is delegated to a log writer.
To log data in a Slim application, get a reference to the log object:
<?php
$log = $app->log;
The log object provides the following PSR-3 interface
$app->log->debug(mixed $object);
$app->log->info(mixed $object);
$app->log->notice(mixed $object);
$app->log->warning(mixed $object);
$app->log->error(mixed $object);
$app->log->critical(mixed $object);
$app->log->alert(mixed $object);
$app->log->emergency(mixed $object);
Each log object method accepts one mixed argument. The argument is usually a string, but the argument can be anything. The log object will pass the argument to its log writer. It is the log writer’s responsibility to write arbitrary input to the appropriate destination.