#42641 [Opn]: ob_start(): inconsistent behaviour with undefined callbacks

ID: 42641 User updated by: robin_fernandes at uk dot ibm dot com Reported By: robin_fernandes at uk dot ibm dot com Status: Open Bug Type: Output Control Operating System: Windows PHP Version: 5CVS-2007-09-12 (snap) New Comment: OK. On this subject, I think I'm running into a few other output buffering issues which seem to be fixed in the php6 snaps. Some of these are illustrated by tests in HEAD that fail on php5 snaps, e.g. http://lxr.php.net/source/php-src/tests/output/ob_017.phpt . Should I raise bugs against php5, or is there a plan to backport some output buffering code from HEAD to php5? Previous Comments: ------------------------------------------------------------------------ [2007-09-13 19:05:24] mike@php.net This undocumented behaviour does not exist in any way in HEAD any longer. The implementation seemed questionable, as an array as parameter usually indicates a method callback. ------------------------------------------------------------------------ [2007-09-13 09:22:07] jani@php.net Yeah, now that I took a closer look I can see there's something like this implemented..I wonder when/why. :) Please don't open documentation issue yet. ------------------------------------------------------------------------ [2007-09-12 14:06:29] robin_fernandes at uk dot ibm dot com Hi, Thanks for your reply. As documentation isn't always complete/up to date, I looked at the implementation of ob_start() to understand its behaviour. The code in the 5.2 version of php_ob_init() in output.c splits strings on ',' and attempts to process each part seaparately (line 485). For arrays, if a pair does not represent a method, a comment explicitly states "init all array elements recursively" (line 516). The prototype in the 5.2 code currently looks like this: bool ob_start([ string|array user_function [, int chunk_size [, bool erase]]]) The following testcase shows this behaviour in action: http://pastebin.com/f4f15a025 Regarding tuning up the error message display params, I'm currently using: error_reporting = E_ALL | E_STRICT / display_errors = 1 . Would you expect see warnings/notices with my testcase? I'll happily raise a documentation bug to ensure this is covered. Alternatively, perhaps the fact that this behaviour is available is itself a bug? Note that this is raised against php5 (not 6 where the output buffering implementation seems to be a bit different). ------------------------------------------------------------------------ [2007-09-12 11:17:04] jani@php.net Let's start with the prototype for this function: bool ob_start ( [callback $output_callback [, int $chunk_size [, bool $erase]]] ) The first parameter is "callback" type, so it expects either a string (function name) or array (object, method). More information about "callback" pseudo-type: http://www.php.net/callback I don't know where you got the idea that you can pass multiple callbacks in there. It's not said to work like that anywhere in the manual at least. :) Please fix your example script accordingly (and tune up your display_errors / error_reporting levels..). ------------------------------------------------------------------------ [2007-09-12 09:15:35] robin_fernandes at uk dot ibm dot com Description: ------------ ob_start() can initialize multiple output buffers in a single call using a comma delimited list of output callbacks, as follows: ob_start('f,f,f'); where function f() is a defined function. However, behaviour when passing an undefined callback is inconsistent: ob_start('non_existent,f'); returns false and initializes no output buffers, whereas ob_start('non_existent,f,f'); returns true and initializes 2 output buffers with f as a callback. Using arrays, the behaviour is consistent. The following both return false and initialize no output buffers: ob_start(array('non_existent', 'f')); ob_start(array('non_existent', 'f', 'f')); Tested on Windows XP on PHP 5.2.5-dev (cli) (built: Sep 12 2007 04:04:36). Reproduce code: --------------- <?php function f($str) { return $str; } function checkAndClean() { print_r(ob_list_handlers()); while (ob_get_level()>0) { ob_end_flush(); } } var_dump(ob_start(array('non_existent', 'f'))); checkAndClean(); var_dump(ob_start(array('non_existent', 'f', 'f'))); checkAndClean(); var_dump(ob_start('non_existent,f')); checkAndClean(); var_dump(ob_start('non_existent,f,f')); //bug: expecting false with no output buffers. Actually returns true and initialises 2 output buffers. checkAndClean(); ?> Expected result: ---------------- bool(false) Array ( ) bool(false) Array ( ) bool(false) Array ( ) bool(false) Array ( ) Actual result: -------------- bool(false) Array ( ) bool(false) Array ( ) bool(false) Array ( ) bool(true) Array ( [0] => f [1] => f ) ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=42641&edit=1