I had not changed anything in my site, But I can not access to any part of the site. I can login but after logging in, I have not any access to any part of my site. I have not access to admin area, too. Without login, anybody can see all parts.
Xoops ver. 2.2.4
Apache Version : 2.2.22
PHP Version : 5.3.1
MySQL Version : 5.5.24

I did the following, but the problem have not solved:
1-I removed all files in templates_c, cache
2-The same problem occurred in localhost.
3-I tried to upgrade to Xoops 2.5.5, But in the upgrade page, the admin username and pass did not work and nothing happened.
4-The errors are:
Unknown Condition [8192]: Function set_magic_quotes_runtime() is deprecated in file \include\common.php line 63
Unknown Condition [8192]: Assigning the return value of new by reference is deprecated in file \include\functions.php line 578
Unknown Condition [8192]: Assigning the return value of new by reference is deprecated in file \include\functions.php line 612
Unknown Condition [8192]: Assigning the return value of new by reference is deprecated in file \kernel\object.php line 744
Unknown Condition [8192]: Assigning the return value of new by reference is deprecated in file \kernel\module.php line 1343

Thank you

You may want to verify your current versions of php.

Sounds like your php was upgraded and now your system isn't working and you will either need to go back to the previous PHP or upgrade to 2.5.5.

With the 2.2 series I will wait for mamba or someone to comment further but I believe that is a dead end branch and is not a simple upgrade. (As in it was abandoned and they started again from the 2.0.17 branch. Which means the 2.3.3 and all newer branches are a totally different system from 2.2)

Thank you
I tried with Apache 2.2.9 and PHP 5.2.6 but the problem was not solved.
The thing is I have not access to admin area and I can't upgrade. My site is about 7 years old and I have a lot of members and etc. What can I do with my site?

Can you try php 4?

Before you do much more you will want to backup all of your files and your database. (Use phpmyadmin or whatever your server has available to backup your data.)

What modules do you have on this system?

Inside your "modules" directory there should be a directory for each installed module.

I found that the problem was my database. I used an old version of my database and it works.
I upgraded to xoops 2.5.5 but these warning are appear:

Warning: Cache Engine file is not initialized in C:\wamp\www\Keshavarz\class\cache\xoopscache.php on line 179

Warning: Cache Engine file is not set in C:\wamp\www\Keshavarz\class\cache\xoopscache.php on line 137

and in some pages this error:
SCREAM: Error suppression ignored for

What are the reasons for these warnings and errors?
In blocks admin page, I can't see any block. I can't add any block. All blocks are removed after upgrading.

After reading this post and changing \ with / in mainfile.php, the warnings disappeared.
Now, one of my problems is that I can not see any block in admin area and when I want to add a block, the xoops says: Errors, None.