Totally confused by this one...
We have a WAMPServer installation set up, running a number of virtual hosts from various document roots.
Just recently, one particular domain has started hanging the server. We traced it down to session_start(). If we comment it out, there are no problems (except, of course, for the fact that we can't do anything with the session). With it uncommented, it will hang the page load and, with enough reloads, will hang the entire server.
All of the other sites still work perfectly with their sessions. As far as I know, there is nothing different with the way sessions are being worked with. I am looking further into it (in case someone changed something) but right now I'm hoping for some direction :)
So, any thoughts?
So, I'm guessing that it's an application layer problem because the other sites' sessions are working properly. However, this assumes that they have their sessions configured the same way - save yourself some time by double checking that your site isn't doing some "unique" in its configuration compared to the other sites.
I would next examine the other session related code that is running in your application. It could be that by calling session_start() you're putting your application into a state where it will run other code. For example, maybe there's a block of code that says "only run this function if this session variable is set" and by starting the session you're exposing that variable, where it wouldn't have been exposed and therefore not run the offending function if the session wasn't started.
Good luck.
My first guess would be file permissions if you are using file based sessions. If you are using database sessions, then I would check to make sure a table isn't corrupt. Also, is it Apache, PHP or something else that's locked up?
It's possible that you hit a bug in your underlying infrastructure that you won't be able to resolve. You should at least clear all existing sessions before moving forward with trying to diagnose this.
Related
I got a really strange problem in my PHP webapp.
If I log in, everything works fine for the duration of my session.
If I come in the next day, my webapp returns me to the Login page (as I expect).
The problem is that once I log in, parts of my site work and parts don't. The parts that don't return strange error messages and then I'm logged out and need to log back in. The strange thing is that some days some parts don't work and other days other parts don't work. If I delete all cookie values I can see, that doesn't solve the problem. The problem is only solved by deleting the entire cookie itself and then logging in again.
I've turned off garbage collection (because on Ubuntu there is supposedly a cron job which does it automatically even though I can't see it) but the issue was occurring before that.
So in terms of simplicity my intention is two-fold:
- To add code to my Login page to delete the cookie entirely (assuming I can do that from PHP)
- To move session storage from my webserver to my MySQL DB (because I'm in my dev environment but preparing to build my test environment which will be a cluster of webservers, not just one)
My questions are:
- Is there any way to ensure session values die reliably and gracefully rather than lingering and wreaking havoc?
- Is it possible to delete an entire cookie from PHP code, rather than just cookie values?
Many thanks.
After being a constant problem for a while, this issue has gone away. I've actually determined the cause and so I thought I'd post a quick update. Basically I had three sites I was accessing on my domain, my own webapp, a CMS Admin page and another admin tool. I've determined that the session cookies between my webapp and CMS admin were interfering with each other. If I use different browsers to access the different sites, the problem doesn't reoccur. It was driving me up the wall. Thanks to those who posted suggestions/responses. I appreciate it. I'll mark this as closed.
I spent about 45 minutes yesterday trying to research and troubleshoot this, so hopefully someone has another idea I can try.
It started out with one of my PHP scripts detecting that the session $_SESSION was empty, so it stopped executing the rest and threw an error for me.
This entire project has worked on that server for at least half a year without any problems, and no update to code or server has been made since then.
Here's what I did then:
I created a new PHP file for testing, made sure there was nothing before or after the <?php ?> container, and wrote this code:
session_start();
var_dump($_SESSION);
$_SESSION['test'] = 5;
Then I ran the file by itself repeatedly, and it always came up with an empty session.
I had run into this before, so I checked the folder where the session files are located on the server (in my case /var/lib/php5), made sure it had the correct directory owner and permissions, deleted all the files in it and restarted apache.
No dice...
I ran the file again a few times, and each run created a NEW session file, and the session file did contain the test=5 entry, so sessions do write correctly.
So I checked the browser cookies. They are there and working as far as I can tell - both the phpsessid cookie and another cookie my site creates were there. If I delete all cookies and then run my test file again, the phpsessid cookie is recreated normally and does contain the same session id that was created as a session file.
I also added var_dump(session_id()); to the code right after session_start();, and it gave me a brand new session id every time the script ran.
We're running a PHP version that does not support session_status() yet, so that's not an option, either (not sure exactly what it would do, anyway, I'm flying rather blindly here).
So, we know sessions are created properly, the files contain the data, the cookie contains the correct id.
So as far as I can tell, the issue must lie either with the browser not sending the cookie data back to the server or the server not recognizing the session id from the cookie as an existing session.
While I was testing this, Firefox wanted to install an update, so I ran the update, but no change.
Firefox is set to receive cookies, and I did not find any exception set anywhere that would prevent them.
Given that this has been working fine for over 6 months, some freak accident must have corrupted something, but I don't know enough about Linux or the internal workings of PHP and sessions to even know where the start diagnosing.
At some point I did try session_write_close() which didn't change anything (and my whole project has always been working fine without it).
The ONLY thing that worked was this:
$c = $_COOKIE['phpsessid'];
session_name($c);
session_start();
var_dump($_SESSION);
$_SESSION['test'] = 5;
But I use session_start in a ton of pages and don't want to go through all of them to enter code that I shouldn't need in the first place...
Any thoughts?
Thanks in advance!
--- EDIT ---
I checked into the issue again, and I can confirm that the cookie name is phpsessid instead of PHPSESSID (thanks for pointing that out, #Cobra_Fast), so that is getting closer to the cause of the issue. I went into the php.ini file to put the value for session.name into quotation marks, then restarted apache, but still no change - the cookie name is still lower case. I haven't found an antivirus program on the computer, and I doubt that there's any network security that could do this... If the PHP settings are corrupted as #Cobra_Fast suggested, how could this be fixed? Editing the file just now didn't help...
After testing some more, we found a really weird thing:
Only one client computer was affected by this! We ran the code on another computer, and it worked normally, and the session cookies are written and read properly.
So it was not the server acting up at all!
I have no clue how this one computer could be just converting cookie names to lower case - it makes no sense at all, especially because it happens in two browsers...
But at least we have a "fix" for the situation, and it's out of our hands since they immediately said they were going to check that computer and re-install it if needed.
I am so majorly confused about this right now, but at least it's over :-)
Thanks for your responses!
I've been trying to track down some annoying session issues since my webhost upgrade to PHP 5.3.3 awhile back. I've determined that if there is an active session, calling session_start() from a subdirectory kills the existing session. As an example, I start a session and a user logs in to domain.com/index.php then the user navigates to domain.com/members/ which fires start_session() ... the user's session is lost.
I've dug around for this and can't find anything similar. Is there a PHP configuration that would account for this behavior?
Calling session_start() multiple times with that version of PHP shouldn't cause any problems, however there are other possible causes.
One possible explanation is that the client's browser isn't sending the session id back to the server. You can test this out by comparing the session id that both pages produce. Assuming that you have a controlled environment where you can test this properly, you can use session_id() to get the session.
It might also be that the user is hitting a different webserver. Since (by default) PHP stores sessions to disk, there is no way for multiple servers to share the session information. If this is a shared host, it's probably quite unlikely this is the cause. You can test this out however by using phpinfo(). It should give you enough information to determine if it's the same server or not. For multi-server systems, I'd look at storing sessions in memcache or mysql.
if your sessions works all right within the same directory (it is unclear from your question), there is the only possible reason for such a behavior, a pretty obvious one: "directory" cookie parameter.
It seems it is set to somewhat unusual value, other than default "/" for the session cookie parameter.
You have to check it out.
Anyway, it is almost useless to try ANY session/cookie related problem without an HTTP interchange log.
You have to use some HTTP sniffer, like LiveHTTPHeaders Firefox addon to see what cookie header was sent by the server and which one was returned by client.
Otherwise it's all going to be shooting in the dark.
Okay, as it seems from your yonder comment, the session id remains the same, so, no HTTP issue can be a reason. The issue become a kinda tricky to spot.
Could you please post your test script here?
I've spent quite a long time searching, trying, testing for what looked like the same problem. As google kept sending me here, I think sharing the solution might help others (though I feel strange posting on a 2011 question):
Session variables set in /bar.php were not set in /foo/foobar.php.
It realised that the issue had nothing to do with folder/subfolder when I finally found out that the link in http://www.example.com/bar.php was pointing to http://example.com/foo/foobar.php (missing www).
Correcting the URL in the html link solved the problem. Having no time to dig deeper, what I can figure out is that (in my config) Apache makes no difference and serves pages indifferently with and without www, whereas PHP doesn't share the session between what it considers being two different domains, example.com and www.example.com.
Is there a PHP configuration that would account for this behavior?
Yes, if the storage for the session data differs between those calls, the $_SESSION content will differ as well. The storage can be configured, see http://php.net/manual/en/session.configuration.php for all configuration options you have with sessions.
Next to that if PHP is unable to read the session store, you will get an empty array as well.
I can't tell you if this is the issue with your problem, but probably it's helpful.
BTW, calling session_start() and than having an empty $_SESSION is commonly a sign that a new session has been created. You can verify this if you use cookies for your sessions and you output headers_listDocs:
echo '<pre>', var_dump(headers_list());
If it contains a new cookie for the session, the session has been created with this request.
Lots of good suggestions here. Thanks everyone. I spent a good chunk of the weekend digging into this and wasn't able to directly resolve it. I ended up demonstrating to my webhost that this problem happens on two of his hosted sites and doesn't happen in a default install of PHP. To work around the problem, I ended up moving all of my login and session logic into a single class.
Wanted to share another answer, found in this SO: Session variables not accessible in subdirectory answered by clayRay.
My answer was that I had a custom "php.ini" file saved in the root directory, and moving those directives into ini_set() calls solved it. You could also shove those over to .htaccess if your host allows.
I'm not quite sure how to phrase this question correctly, so I'll start with the scenario I encountered.
I have a bit of processing in my web app that takes longer than I'd like the user to wait to have control of the page again, so I decided to have it processed by an ajax request.
The problem is, even though I offloaded this request into an ajax request, it seems that apache won't process any further requests until the original processor heavy request is complete.
I originally wanted to know how I could get around this issue, but have since decided that it might be a bad idea in general.
However, I'm still curious if anyone knows why apache behaves this way, and what (if any) configuration directive controls it. My original thought was KeepAlive, but disabling that didn't seem to change the behavior.
I am running php through mod_php if that makes a difference.
I appreciate any help getting pointed in the right direction!
Are you using file-based sessions? PHP will lock session files for each request and maintain that lock until you do a session_write_close() or the script terminates/exits. The side effect of this is that all requests become serial, since they're all contending for the same single resource (the session file).
I am sure it's the session file. I have the same problem. I run a request that is long such as a PHPMyAdmin SQL insert which takes multiple minutes to process. While it is processing I try to open a new tab in the same browser and go to any page on my website and it will not go there until the original PHPMyAdmin request is done.
If I open an incognito window in Chrome which is the same browser it works fine. If I open the website in any other browser it is fine.
So it is probably the file based session which is the default for PHP.
Others have mentioned going to memcached. You could also save sessions in the database.
Before having to go to memcached you could do all the session based stuff at the beginning. Copy the session variable into a temporary variable so you can close it then close it. And then if you need to set a session value later open it and make the change and then close it quickly.
Can you point to evidence that it's apache? Unless your apache setup isn't optimal, most likely your page wait is something else, maybe you have set your ajax call to be non-async?
I'm not exactly sure the question I should be asking. Sorry!
I'm working on re-doing my web site so as to be using PHP5. The server lives in a buddy's basement and I just ssh in to do my coding and view the pages just like any other page out there.
I keep track of login details in $_SESSION.
When I'm sitting at my home machine I can log into the site and everything is as I expect it in terms of the SESSION being available on all pages. When I log in on my work machine, I get a successful log in and can see the SESSION variables, but as soon as I go to another page the SESSION is gone as evidenced in session_id().
My previous web site built in PHP4 (and tweaked to keep PHP5 happy) does not exhibit this behavior allowing me to log in as expected at either location before and after the change to PHP5.
I guess I'm just looking for a clue as to what to explore next... Of all the puzzles I've encountered while teaching my self to code this one appears on the face, just crazy.
I think Jake is on to something about the cookies. Make sure your browser at work is set to accept cookies from that domain. Make sure there isn't any antivirus/antimal-ware that has disabled this. I'd use fiddler to watch the traffic and headers on your work machine, and your home machine. you should be able to quickly spot the difference since it sounds like a client issue.
It could be that the computer at work isn't supporting session cookies. It's been a while since I last read about PHP Sessions, but from what I remember...
session_start() is called.
php checks to see if the browser has sent a cookie to the server (a unique identifier needs to be supplied.
if so, it then checks checks on the server for a file with the name of the session id
if successful, it parses the file and sets the variables into the $_SESSION array
Notice that step one of this process is to actually start the session with session_start() this needs to be called before any output at all.
Have you got session_start() before output?
Do you make use of session_start() in your various php files ?
One way to get around this problem could be to store your sessions in a database.
This DevShed article by Rich Smith is a good place to start:
Storing PHP Sessions in a Database
The session is no longer saved as a file on the server, but rather an entry in the DB, and should solve any cookie issues.
Are the settings in php.ini for session.auto_start the same in both ini's?
See http://de3.php.net/manual/en/session.configuration.php#ini.session.auto-start