After upgrading PHP to version 5.3 on Windows shared hosting server customers' web sites that used PHP as ISAPI, the extension breaks. On attempt to open any PHP script, the following message is returned by IIS:
HTTP Error 500 - Internal server error
Support for the ISAPI module is dropped in PHP 5.3. Refer to the following article on the PHP website for more information: http://www.php.net/manual/en/migration53.windows.php
Before upgrading PHP on a POA-managed Windows shared hosting server to version 5.3, it is necessary to switch all customers' web sites into FastCGI mode. This can be done in the POA Customer Control Panel:
Go to Websites > Choose WebSite name > WebSite Configuration
Change the value of the "PHP support" parameter to "Run as FastCGI application"