After reading some PHP source as well as the PHP manual we have arrived at the following two situations with one conclusion: * SAPI supports flush(): o call to flush() is enough to stop the page from displaying as loading o and thus register_shutdown_function is unnecessary * SAPI does not support flush(): o neither a call to flush() nor the beginning of shutdown phase, which calls registered shutdown functions can flush anything to the client o and thus register_shutdown_function is unnecessary Thanks to lacton for reporting the initial issue. Thanks to nn- and naderman for doing all the dirty works. PHPBB3-10046