Output Buffering handler: Manage multiple handlers to filter the page output

This class can be used to manage multiple filters that can filter the output of the current script.

It enables the script output buffering in such way that the output will be filtered by handler code managed by the class.

The class can add multiple handlers that will process the output one after another.

The handler code is treated as PHP code template that is executed to process the output and return the filtered output.