DoctrineExtensions\Query\SortableNullsWalker::walkOrderByItem PHP Method

    public function walkOrderByItem($orderByItem)
    {
        $sql = parent::walkOrderByItem($orderByItem);
        $hint = $this->getQuery()->getHint('sortableNulls.fields');
        $expr = $orderByItem->expression;
        $type = strtoupper($orderByItem->type);
        if (is_array($hint) && count($hint)) {
            // check for a state field
            if ($expr instanceof Query\AST\PathExpression && $expr->type == Query\AST\PathExpression::TYPE_STATE_FIELD) {
                $fieldName = $expr->field;
                $dqlAlias = $expr->identificationVariable;
                $search = $this->walkPathExpression($expr) . ' ' . $type;
                $index = $dqlAlias . '.' . $fieldName;
                $sql = str_replace($search, $search . ' ' . $hint[$index], $sql);
            }
        }
        return $sql;
    }