I ran into a very annoying problem two days ago, regarding PHP sessions, as it seems they don't persist through pages, and the session\_start(); function starts a new session rather than resuming the existing one. This even happens on reloads. 

Here's how the session section in my php.ini looks like. 

```
Session Support     enabled
Registered save handlers    files user
Registered serializer handlers  php php_binary wddx 

session.auto_start  Off Off
session.bug_compat_42   Off Off
session.bug_compat_warn Off Off
session.cache_expire    180 180
session.cache_limiter   no value    no value
session.cookie_domain   no value    no value
session.cookie_httponly Off Off
session.cookie_lifetime 0   0
session.cookie_path /   /
session.cookie_secure   Off Off
session.entropy_file    no value    no value
session.entropy_length  0   0
session.gc_divisor  1000    1000
session.gc_maxlifetime  1440    1440
session.gc_probability  0   0
session.hash_bits_per_character 5   5
session.hash_function   0   0
session.name    PHPSESSID   PHPSESSID
session.referer_check   no value    no value
session.save_handler    files   files
session.save_path   /tmp    /tmp
session.serialize_handler   php php
session.use_cookies On  On
session.use_only_cookies    On  On
session.use_trans_sid   1   1

```

I'm running an Ubuntu server, and the www-data user has got writing and reading permisions on the /tmp folder. The session files exist, but it chooses to start a new one for some reason. 

OS : Ubuntu 12.04 
PHP Version : 5.3.1
Web server : Apache 2.2

Thank's in advance for any suggestion or piece of advice, and, of course, for your time !

[PROBLEM SOLVED]

Problem solved, I had to set the cookie domain to "example.com" (replace with your own domain) and make sure I make my redirections to "exemple.com/bla/bla" rather than "www.exemple.com/bla/bla".