addon_builder.php

    public function composer_field_order( $form_id ){
        $composer = ee()->db->select('composer_id')
            ->where('form_id' , $form_id)
            ->get('freeform_forms')
            ->row()
            ->composer_id;

        $layout = ee()->db->select('composer_data')
            ->where('composer_id' , $composer)
            ->get('freeform_composer_layouts')
            ->row();

        if ( $layout ) {
            $layout = json_decode( $layout->composer_data );
            $order = array();

            foreach ( $layout->rows as $row ) {
                foreach ( $row as $fields ) {
                    foreach ( $fields as $field ) {
                        if ( isset( $field->fieldId ) ) {
                            $order[] = $field->fieldId;
                        }
                    }
                }
            }
            return $order;
        }
        return false;
    }