This is a quicky: If you have Windows Vista and XAMPP and your “CLI has stopped working” you need to download the PHP binaries (Windows Binaries, zip package) from php.net and replace the php_mysqli.dll in C:\xampp\php\ext with the version you just downloaded. Downloading the latest version of PHP should work just fine, even if an older version was previously installed on your system. – I know this seems weird, but it works. If you want a longer explanation, read Tengku Zahasman’s article on the same subject, with the comments. (I found the article using Google.)