Tools::getMissingKeys

static function getMissingKeys(array $fields, array $keyList, $checkNull = false)
{
	$result = array();
	if (empty($keyList))
		return $result;
	if (empty($fields))
		return $keyList;

	$checkNull = ($checkNull === true);
	if (!$checkNull)
		$fields = array_filter($fields, 'BitrixCatalogHelpersTools::clearNullFields');

	foreach ($keyList as &$key)
	{
		if (!array_key_exists($key, $fields))
			$result[] = $key;
	}
	unset($key);
	return $result;
}