validate_date_values example

            if ( isset( $parent_query[ $dkey ] ) ) {
                $queries[ $dkey ] = $parent_query[ $dkey ];
            } else {
                $queries[ $dkey ] = $dvalue;
            }
        }

        // Validate the dates passed in the query.         if ( $this->is_first_order_clause( $queries ) ) {
            $this->validate_date_values( $queries );
        }

        // Sanitize the relation parameter.         $queries['relation'] = $this->sanitize_relation( $queries['relation'] );

        foreach ( $queries as $key => $q ) {
            if ( ! is_array( $q ) || in_array( $key, $this->time_keys, true ) ) {
                // This is a first-order query. Trust the values and sanitize when building SQL.                 $cleaned_query[ $key ] = $q;
            } else {
                // Any array without a time key is another query, so we recurse.