Symptoms
The website is displaying an "Internal error":
HTTP Error 500.0 - Internal Server Error
C:\Program Files (x86)\Parallels\Plesk\Additional\PleskPHP53\php-cgi.exe - The FastCGI process exited unexpectedly
'php-cgi.exe -v' fails with the below warning:
PHP Warning: PHP Startup: Unable to load dynamic library 'C:\Program Files (x86)\Parallels\Plesk\Additional\PleskPHP53\ext\php_interbase.dll' - The specified module could not be found.
Cause
'C:\Program Files (x86)\Parallels\Plesk\Additional\PleskPHP53\ext\php_interbase.dll' requires a 'fbclient.dll' library, which is not present on a Windows servers by default.
Resolution
Either install Firebirdsql package, or comment out the following extension in PHP configuration file ('C:\Program Files (x86)\Parallels\Plesk\Additional\PleskPHP53\php.ini'):
;extension=php_interbase.dll
NOTE: In the above example we assumed that PHP 5.3 is used. In case if you use a different version, modify the 'php.ini' i na corresponding location.