Bug #12267: Session (concurrency ?) problem

From: thomas.morin@webmotion.com Operating system: Linux PHP version: 4.0.6 PHP Bug Type: Unknown/Other Function Bug description: Session (concurrency ?) problem While testing a php apllication, I found that I had some trouble with session variables (php4 native sessions, not phplib's crappy ones), at this point I was using a custom MySQL session handler (with session_set_save_handler). After adding some error_log calls in my custom session handler functions, I managed to see that the problem was coming from the fact that a session was reopened before the current one was written to the database : (in chronological order) request A request B HTTP request A is made on page1.php session open by session_start: session variable A equals 0 request A is being treated: session variable A is set to 1 redirection is made with header() to page2.php ------------------> request B is made on page2.phpA exit() session open by session _start session variable A equals 0 treatment made by my application: no change to make to variable A if variable A is 0 php saves the session => A is stored with value 1 exit() php saves the session => A is stored with value 0 And in the end, A ends up being 0, which is not what it should be. I found a way of making the bug go away (for a moment) : make a sleep(2) in my session 'open' handler. :))) This "solved" the problem and I concluded the bug was only due to my fault : I should have locked my session table (or row...) to avoid race conditions and concurrency problems. Then I thought that such a locking should have been done by the php session layer itself, because this issue is common to all session handlers you can use or define. And I found in the online documentation session_end and session_readonly which seemingly were tackling with similar concurrency issue, and I concluded this was worked on and would probably be solved in some next release, but php 4.0.6 doesn't solve the problem, and the session_end and session_readonly functions - though they appear in the documentation - are not even appearing in the CVS code. So my question : is this really a known issue ? is a fix for this planned soon ? Thank you !! -- Edit bug report at: http://bugs.php.net/?id=12267&edit=1