WC_Product::add_to_cart_url PHP Method

    public function add_to_cart_url()
    {
        return apply_filters('woocommerce_product_add_to_cart_url', $this->get_permalink(), $this);
    }

/**
 * Get the add to cart URL for a product
 **/
function woocommerce_product_add_to_cart_url($atts)
{
    if (empty($atts)) {
        return;
    }
    global $wpdb;
    if ($atts['id']) {
        $product_data = get_post($atts['id']);
    } elseif ($atts['sku']) {
        $product_id = $wpdb->get_var($wpdb->prepare("SELECT post_id FROM {$wpdb->postmeta} WHERE meta_key='_sku' AND meta_value='%s' LIMIT 1", $atts['sku']));
        $product_data = get_post($product_id);
    } else {
        return;
    }
    if ($product_data->post_type !== 'product') {
        return;
    }
    $_product = new WC_Product($product_data->ID);
    return esc_url($_product->add_to_cart_url());
}