The WinCache extension requires PHP to be compiled with the "Thread Safety" feature disabled. Only PHP 5.4, which is included in the Parallels Plesk 11.0.9 release, is built this way. The WinCache extension can also be installed and enabled for PHP 5.4.
To enable the WinCache extension, download the WinCache extension for PHP 5.4 from http://sourceforge.net/projects/wincache/files/ and install it in the
ext subdirectory of the PHP 5.4 directory,
Then add the following line into the file
Installing a PHP WinCache extension will not affect Parallels Plesk Panel since Plesk uses a separate installation of PHP (see KB article #115836).