Typoscript Condition that checks field up in rootline

levelFieldCondition.php

<?php

/**
 * Usage example: [userFunc = levelFieldCondition(layout=1)]
 *
 * @param string $assumption
 * @return bool
 */
function levelFieldCondition($assumption) {
	list($fieldname, $value) = t3lib_div::trimExplode('=', $assumption);
	foreach($GLOBALS['TSFE']->rootLine as $rootlinePage) {
		if($rootlinePage[$fieldname] !== NULL) {
			return $value == $rootlinePage[$fieldname];
		}
	}
	return strtolower($value) === 'null';
}

?>