protected static function attribute_condition($quoted_column_name, $value) { if ($value === null) { return $quoted_column_name . ' IS NULL'; } else { if (is_array($value)) { return SqlBuilder::sanitize_sql($quoted_column_name . ' IN (?)', $value); } else { return SqlBuilder::sanitize_sql($quoted_column_name . ' = ?', $value); } } }