Hi,
If you've installed PHP through Web PI, then your PHP installation is located at C:\program files (x86)\PHP (assuming C:\ is your system drive).
Are you editing the php.ini file located at C:\PHP\php.ini or the one at C:\program files (x86)\PHP\php.ini? Please make sure it is the latter.
If it is indeed the latter, could you also try to put the lib*.dll files in the same location as the ini file (C:\program files (x86)\php).
Lastly, you should recycle the PHP processes to pick up the changes immediately or wait until the appropriate timeouts occur.
All the PHP directory locations (including the location of the ini file being loaded) can be found in the phpinfo() page.
HTH,
Kern