Not able to add product to cart on magento website in subfolder

[stefan7299]

I've been searching all over to find a solution to our issue. We are running a magento marketplace (1.9.2.2) with multiple magento websites as subfolders:
domain.com/website1
domain.com/website2
etc..
Each website has a store view.

Issue: I can add products to the cart in the default website (domain.com), but adding products from the magento websites/stores running in the subfolder, does not work. The message: The cart is empty....

Checked:
- system.log file (no error as far as I can tell)
- cookies are set (tried all kinds of configurations), currently life set to 3600 (tested 86400), other options are default settings (empty), but tried also with setting various cookie domains, -> no effect
- customer data shared globally
- prices set per website
- products released for all websites/stores
Followed this tutorial for multi store setup:

https://www.hostknox.com/tutorials/magento/multistore

I really run out of any ideas why it does not work.
What could prevent adding products to the cart if the website/store is in a subfolder?

[stefan7299 · Accepted solution]

Resolved thes in the meantime. Found the culprit after checking the exception.log file whre this error was shown: 'Zend_Cache_Exception' with message 'cache_dir "tmp/" must be a directory' in /xxx/xxx/magento_staging/lib/Zend/Cache.php:209

Found the answer about the error here: https://stackoverflow.com/questions/16031456/message-cache-dir-must-be-a-directory

It seems that due to the subfolder configuration, the path in file.php in lib/Zend/Cache/Backend/ on line 98 needs to be adapted. Like so:

protected $_options = array(
        'cache_dir' => '/your/path/magento_staging/tmp',