会话变量在PHP5 / Apache2 / Ubuntu12中不持久

Question

I couldn't find this specific problem around. I have a website that uses session variables (in PHP) to know if the visitor is entering the website or not. If he's new, then I redirect him to the detected language. But if he's not new, you let him go wherever he wants to (even the pages in other languages).

The problem is that the variable used to achieve this ($_SESSION["knownvisitor"]) is not persistent. I've tested the same website in other server and it works just fine, so I'm pretty sure it's a sessions config problem. The problematic server is an Ubuntu Server 12.04.4 with Apache 2.2.22 and PHP 5.3.10.

The sessions are stored in /var/lib/php5 , and I can see the files there but they are empty. The session files belong to www-data and have the following rights -rw------- . The directory, in the other hand, belongs to "root" and has these rights drwx-wx-wt .

I tried using session_write_close() before redirecting, as recommended in some forums, with no luck. The redirection is like header('Location: [URL]') .

Does anyone have a clue? Thank you!

EDIT: I'll add the code of the script so you can understand it's basic behaviour. This is what I put in the beginning of all the files in my web:

function detectedlang($availlangs)
{
 // FUNCTION STUFF HERE TO FIND OUT WHICH IS THE LANGUAGE OF THE VISITOR
 return $detectedlang;
}

session_start();

if (!isset($_SESSION["knownvisitor"]))
{
 $detectedlang = detectedlang(array("en", "es"));
 $_SESSION["knownvisitor"] = true;
 header("Location: http://www.mysite.com/".$detectedlang);
}

Answer 1

A session only lives for as long as defined in session.gc_maxlifetime I think 20 minutes is the default

If you want to check for a returning visitor you'll need to set a cookie

Answer 2

检查session.save_handler : files也使用error_reporting(E_ALL);

Answer 3

I got it solved thanks to the good people of serverfault.com. The problem is that the folder /var/lib/php5 is owned by root and can't be read by anyone else ( drwx-wx-wt ). This is why PHP (user www-data ) can't access and retrieve the session data from the file there.

A simple change in groups and permissions got it running:

chgrp www-data /var/lib/php5
chmod g+rwx /var/lib/php5

In other words, change the group of the directory to www-data and allow its members to read the contents.