PHP has some nice features to do output buffering. You just call ob_start() and anything you output (except headers) does not actually get set back to the webserver (and thus the browser) until you decide it. As the manual puts it "This can be useful in several different situations, especially if you need to send headers to the browser after your script has began outputting data."
One particular use of this feature is to pass an "ob_handler" callback function as an argument to ob_start(). This is supposed to let you do "kewl" post-processing operations like: gzip compression, adding an ETag, adding content-length of your whole output.
Crap!
There are only two situations where ob_handlers are useful:
- When your webserver can't take care of this for you. But you know, you should really consider switching to Apache, which already has modules to handle all that, and even better: unlike PHP ob_handlers, it can do gzip compression progressively without waiting for the whole page to have generated! :crazy:
- When you are in desperate need for marketing arguments to write a book on ~` Advanced PHP '~ ! >:XX