I followed these instructions verbatim, and it still won’t work. I even tried both isapi and the executable in IIS.
https://www.php.net/manual/en/ref.mysql.php
MySQL is no longer enabled by default, so the php_mysql.dll DLL must be enabled inside of php.ini. Also, PHP needs access to the MySQL client library. A file named libmysql.dll is included in the Windows PHP distribution and in order for PHP to talk to MySQL this file needs to be available to the Windows systems PATH.
Don’t get me wrong – I love WordPress, and mySQL, it’s PHP that isn’t playing nice. I’ve never had this much trouble setting anything up – even CFMX!