Turns on output buffering, which causes all output to be
accumulated in a buffer instead of being sent directly to the browser.
callback is specified, it is a function
(called before sending the output buffer to the client) that can
modify the data in any way; the
ob_gzhandler() function is provided to
compress the output buffer in a client-aware manner. The
chunk option can be used to trigger the
flushing of the buffer when the buffer size equals the chunk number.
erase option is set to
false, then the buffer will not be deleted
until the end of the script. See Chapter 13 for more information on using the