If you’re on ExpressionEngine 2 and moving to a new server that does not have PHP 5, you’ll run into some server errors. There are a few options which can get your site working again, one of it is if you install PHP 5. The other option is to add a simple line in your database.php. You can find that file here:
Edit database.php and add replace
$db[‘expressionengine’][‘dbdriver’] = ‘mysql’;
$db[‘expressionengine’][‘dbdriver’] = ‘mysqli’;
and you should be all set.