1- The problem is about PHP-FPM/FastCGI websites. 2- We noticed the problem when we got PHP warnings like: "PHP Warning: file_get_contents(): open_basedir restriction in effect. File(/var/www/clients/client1/web17/web/www/vendor/symfony/ ... /xliff-core-1.2-strict.xsd) is not within the allowed path(s): (/var/www/clients/client1/web1/web:/var/www/clients/client1/web1/private:/var/www/clients/client1/web1/tmp:/var/www/example.com/web:/srv/www/example.com/web:/usr/share/php5:/usr/share/php:/tmp:/usr/share/phpmyadmin:/etc/phpmyadmin:/var/lib/phpmyadmin) in (...) XliffFileLoader.php on line 147" /var/www/clients/client1/web17 is for another website, it should be /var/www/clients/client1/web1 3- This problem occurs especially after creating subdomains. Thanks to the open_basedir restriction, we can notice it in error.log. However, when two subdomains in one single website have duplicated site files and folders, they mingle their codes, i.e., when we clone a site folder and create a new subdomain for the new one, unexpected behaviours occur! For different websites, say, /var/www/clients/client1/web1/index.php is interpreted by PHP as /var/www/clients/client1/web17/index.php. This returns PHP warning, open_basedir restriction. For subdomains in single website, say, /var/www/clients/client1/web1/sub2/index.php is interpreted by PHP as /var/www/clients/client1/web1/sub1/index.php. This does not return any warning, since PHP-FPM users and directories are same. However, sub2.example.com responses as sub1.example.com! But surprisingly, When, I put a dummy comment line at the bottom of the file, /var/www/clients/client1/web1/sub2/index.php, everything works as expected. sub2.example.com responses as it is. We speculate that, since /var/www/clients/client1/web1/sub2/index.php is a copy of /var/www/clients/client1/web1/sub1/index.php, their caches should be same or so. Sincerely, Ali Galip Below are the technical details: ISPConfig Version: 3.0.5.4p8 Operating System: Ubuntu 14.04.3 LTS PHP Version: PHP 5.5.9-1ubuntu4.14 (fpm-fcgi) (built: Oct 28 2015 01:38:24) PHP 5.5.9-1ubuntu4.14 (cli) (built: Oct 28 2015 01:34:46) Copyright (c) 1997-2014 The PHP Group Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies with XCache v3.1.0, Copyright (c) 2005-2013, by mOo with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies with XCache Optimizer v3.1.0, Copyright (c) 2005-2013, by mOo with XCache Cacher v3.1.0, Copyright (c) 2005-2013, by mOo with XCache Coverager v3.1.0, Copyright (c) 2005-2013, by mOo Server version: Apache/2.4.7 (Ubuntu) Server built: Oct 14 2015 14:20:21 Zend OPcache Opcode Caching: Up and Running Optimization: Enabled Cached scripts: 1941 Cached keys: 1957 XCache Cacher Module: enabled XCache Coverager Module: enabled XCache Optimizer Module: enabled