>On Windows, PHP is most commonly installed using the binary installer. Once PHP has been installed, some >configuration is required to enable mysqli and specify the client library you want it to use.
Basically, if you want to add extensions you can double-click again on the installer file. The installer will find the already installed PHP and will ask if you want to change the installation.
When you go through the prompts it will take you back to the list of extensions and you can pick which extensions you want to add.
For the mysqli extension the installer also edited php.ini so that the extension was enabled:
the installer added those lines to the end of the file.