A quick reference for what each log level should be used for.
| Level | Description |
|---|---|
| Emergency | System is unusable |
| Alert | Action must be taken immediately. Example: Entire website down, database unavailable, etc. This should trigger the SMS alerts and wake you up. |
| Critical | Critical condition. Example: Application component unavailable, unexpected exception. |
| Error | Runtime errors that do not require immediate action but should typically be logged and monitored. |
| Warning | Exceptional occurrences that are not errors. Example: Use of deprecated APIs, poor use of an API, undesirable things that are not necessarily wrong. |
| Notice | Normal but significant events |
| Info | Interesting events. Example: User logs in, SQL logs |
| Debug | Detailed debug information |
Reference: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-3-logger-interface.md