After uncommenting extensions

extension=php_curl.dll
extension=php_mhash.dll

in php.ini. I started getting getting Apache errors

PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\\php-5.2.1\\ext\\php_curl.dll' - 
The specified module could not be found.\r\n in Unknown on line 0

PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\\php-5.2.1\\ext\\php_mhash.dll' - 
The specified module could not be found.\r\n in Unknown on line 0

And of course the module would not load. As somebody pointed out there are two ways to make it work:
1. Copying libeay32.dll, ssleay32.dll, and libmhash.dll to C:\windows\system32

Using YAML for configuration file(s) in PHP application seems like a good idea.
There is a YAML parser class already written in PHP. YAML seems to have a bit less overhead than an XML file, and it nicely outputs a PHP array ready for use in the code. Dead simple to use as well.

Small overhead of parsing YAML file is well justified when it comes to updates.