The error message suggests that the first argument passed to the BufferHandler constructor should be an instance of HandlerInterface, but a string was passed instead. To fix this, you need to create an instance of the RotatingFileHandler class and pass it as the first argument to the BufferHandler constructor. Here's an example configuration that should work:
'my_daily' => [
'driver' => 'monolog',
'handler' => Monolog\Handler\BufferHandler::class,
'with' => [
'handler' => new Monolog\Handler\RotatingFileHandler(storage_path('logs/daily-buffer.log'), 100, Monolog\Logger::DEBUG, true, 0664),
'buffer_size' => 100 * 1024, // 100 KB
],
],
In this example, we're creating a new instance of RotatingFileHandler and passing it the log file path, the maximum file size (100 KB), the log level (DEBUG), whether to create the log file if it doesn't exist, and the file permissions. We're then passing this instance as the handler argument to the BufferHandler constructor, and setting the buffer_size option to 100 KB. This should create a buffer that flushes to the log file whenever it reaches 100 KB in size.