public function column(array $src, $column, $skip = false, $skipEmpty = false)
    {
        $result = array();

        // process each row
        foreach ($src as $key => $row) {
            // if current row is an array and the specified column exists
            // store column value otherwise null
            if (is_array($row) && array_key_exists($column, $row)) {
                if (!$skipEmpty || !empty($row[$column])) {
                    $result[$key] = $row[$column];
                }
            } else {
                // skip not existing values ...
                if (!$skip) {
                    // ... or add null
                    $result[$key] = null;
                }
            }
        }

        return $result;
    }