Redundant isset() check?

Consider the situation where an application will use a different set of PDO connection details depending on which version of the site is running: production, dev, qa, cron job, etc. Considering that $_SERVER['DOCUMENT_ROOT'] may not be set, is this check sufficient: if ( !isset( !isset($connection_details[$_SERVER['DOCUMENT_ROOT']]) ) { Or would it be preferable to first check that $_SERVER['DOCUMENT_ROOT'] is set before relying on it: if ( !isset($_SERVER['DOCUMENT_ROOT']) || !isset($connection_details[$_SERVER['DOCUMENT_ROOT']]) ) { The TRUE case of this if clause will simply use the default connection details: $connection_details[0] -- Dotan Cohen http://gibberish.co.il http://what-is-what.com