Sorry missed a line in my previous post, just to make it clear that's
not the cause of the error:
I'm loading the extension from my old
LocalSettings.php like this:
require_once("${IP}/extensions/ConfirmEdit/ConfirmEdit.php");
require_once("${IP}/extensions/ConfirmEdit/ReCaptcha.php");
$wgCaptchaClass = 'ReCaptcha';
$wgReCaptchaPublicKey = 'xxx';
$wgReCaptchaPrivateKey = 'xxx';
Cheers,
Adam.