note 59771 added to function.register-shutdown-function

Could anybody know why redirect is made only after shutdown_function ends? (after 3 sec sleep) Code: register_shutdown_function('sd_test'); function sd_test () { sleep(3); } header('Location: http://php.net'); exit; ---- Manual Page -- http://www.php.net/manual/en/function.register-shutdown-function.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+59771 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes&reason=non-english Delete: already in docs -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes&reason=already+in+docs Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+59771&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+59771&report=yes Search -- http://master.php.net/manage/user-notes.php