woo update variation attribute

variation-attribute.php

<?php 

    add_action('init',  'update_attributes_variation_product');

    function add_variation_product($post_id){
        $cars = array('c1', 'c2', 'c3' );
        $info = array('ww' );
        $att_all = [];
        $att_all['car'] = $cars;
        $att_all['info'] = $info;
        $arr_attr_to_paren_product = [];
        foreach ($att_all as $key => $value) {
            $arr_attr_to_paren_product[$key] = $this->to_string_attribute($value);
        }
        $my_product_attributes = $arr_attr_to_paren_product;
        wcproduct_set_attributes($post_id, $my_product_attributes);

        foreach ($cars as $key_car => $car) {
            foreach ($info as $key_inf => $inf) {
                $_pv = new WC_Product_Variation();
                $_pv->set_parent_id($post_id);
                $_pv->set_manage_stock('true');
                $_pv->set_stock_status('instock');
                $_pv->set_status('publish');
                $_pv->set_regular_price( 50 );
                $_pv->set_sale_price( 50 );
                $_pv->set_menu_order(0);
                // $_pv->set_sku($_sku);
                $_pv->set_stock_quantity(11);
                $ar_attr = [];
                $ar_attr['car'] = $car;
                $ar_attr['info'] = $inf;
                $_pv->set_attributes($ar_attr);

                update_post_meta( $_pv->get_id(), 'attribute_'.'car', $car);      
                update_post_meta( $_pv->get_id(), 'attribute_'.'info', $inf);    
                $_pv->save();
            }
        }

        $data = [];
        $data['attribute_names'] = [];
        $data['attribute_values'] = [];
        $data['attribute_position'] = [];
        $data['attribute_visibility'] = [];
        $data['attribute_variation'] = [];
        foreach ($att_all as $key => $value) {
            $data['attribute_names'][] = $key;
            $data['attribute_position'][] = '0';
            $data['attribute_values'][] = $this->to_string_attribute($value);
            $data['attribute_visibility'][] = '1';
            $data['attribute_variation'][] = '1';
        }
        $attributes   = WC_Meta_Box_Product_Data::prepare_attributes( $data );
        $product_id   = absint( $post_id );
        $classname    = WC_Product_Factory::get_product_classname( $product_id, 'variable' );
        $product      = new $classname( $product_id );
        $product->set_attributes( $attributes );
        $product->save();

    }

function wcproduct_set_attributes($post_id, $attributes) {
        global $superopt;
        $product = wc_get_product($post_id);
        $old_attributes = $product->get_attributes();
        $product_attributes  = [];
        foreach ( $old_attributes as $name => $value ) {
            $product_attributes[] = array (
                'name' => htmlspecialchars( stripslashes( $name ) ), // set attribute name
                'value' => $value, // set attribute value
                'position' => 1,
                'is_visible' => 1,
                'is_variation' => 1,
                'is_taxonomy' => 0
            );
        }
        foreach ($attributes as $name => $value) {
            $product_attributes[] = array (
                'name' => htmlspecialchars( stripslashes( $name ) ), // set attribute name
                'value' => $value, // set attribute value
                'position' => 1,
                'is_visible' => 1,
                'is_variation' => 1,
                'is_taxonomy' => 0
            );
        }
        update_post_meta($post_id, '_product_attributes', $product_attributes);
}
     function to_string_attribute($attr_val)
    {
        $str_arr = '';
        foreach ($attr_val as $key => $val) {

            if ($key == 0) {
                $str_arr = $val;
            } else {
                $str_arr .= ' | ' . $val;
            }
        }
        return $str_arr;
    }