- **ALERT** (550): Action must be taken immediately. Example: Entire website
down, database unavailable, etc. This should trigger the SMS alerts and wake
you up.
- **EMERGENCY** (600): Emergency: system is unusable.
Using
-----
`Log::level(message: string, context: array);`
* The message MUST be a string or object implementing __toString().
* The message MAY contain placeholders in the form: {foo} where foo
will be replaced by the context data in key "foo".
* The context array can contain arbitrary data. The only assumption that
can be made by implementors is that if an Exception instance is given
to produce a stack trace, it MUST be in a key named "exception".
Where Logs are Stored
---------------------
By default, log entries are written to the `var/log/dev.log` file when you’re in the
`dev` environment. In the `prod` environment, logs are written to `var/log/prod.log`,
but only during a request where an error or high-priority log entry was made (i.e. `Log::error()` , `Log::critical()`, `Log::alert()` or `Log::emergency()`).
Example usage
-------------
```php
Log::info('hello, world.');
// Using the logging context, allowing to pass an array of data along the record:
Log::info('Adding a new user', ['username' => 'Seldaek']);