$level
$level : integer
Blackhole
Any record it can handle will be thrown away. This can be used to put on top of an existing stack to override it temporarily.
close()
Closes the handler.
Ends a log cycle and frees all resources used by the handler.
Closing a Handler means flushing all buffers and freeing any open resources/handles.
Implementations have to be idempotent (i.e. it should be possible to call close several times without breakage) and ideally handlers should be able to reopen themselves on handle() after they have been closed.
This is useful at the end of a request and will be called automatically when the object is destroyed if you extend Monolog\Handler\Handler.
If you are thinking of calling this method yourself, most likely you should be calling ResettableInterface::reset instead. Have a look.