private static function add_to_cart_handler_variable( $product_id ) {
		try {
			$variation_id         = empty( $_REQUEST['variation_id'] ) ? '' : absint( wp_unslash( $_REQUEST['variation_id'] ) ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended
			$quantity             = empty( $_REQUEST['quantity'] ) ? 1 : wc_stock_amount( wp_unslash( $_REQUEST['quantity'] ) ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended
			$missing_attributes   = array();
			$variations           = array();
			$variation_attributes = array();
			$adding_to_cart       = wc_get_product( $product_id );

			if ( ! $adding_to_cart ) {
				return false;
			}

			// If the $product_id was in fact a variation ID, update the variables.
			if ( $adding_to_cart->is_type( 'variation' ) ) {
				$variation_attributes = $adding_to_cart->get_variation_attributes();
				// Filter out 'any' variations, which are empty, as they need to be explicitly specified while adding to cart.
				$variation_attributes = array_filter( $variation_attributes );
				$variation_id   = $product_id;
				$product_id     = $adding_to_cart->get_parent_id();
				$adding_to_cart = wc_get_product( $product_id );

				if ( ! $adding_to_cart ) {
					return false;
				}
			}

			// Gather posted attributes.
			$posted_attributes = array();

			foreach ( $adding_to_cart->get_attributes() as $attribute ) {
				if ( ! $attribute['is_variation'] ) {
					continue;
				}
				$attribute_key = 'attribute_' . sanitize_title( $attribute['name'] );

				if ( isset( $_REQUEST[ $attribute_key ] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
					if ( $attribute['is_taxonomy'] ) {
						// Don't use wc_clean as it destroys sanitized characters.
						$value = sanitize_title( wp_unslash( $_REQUEST[ $attribute_key ] ) ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended
					} else {
						$value = html_entity_decode( wc_clean( wp_unslash( $_REQUEST[ $attribute_key ] ) ), ENT_QUOTES, get_bloginfo( 'charset' ) ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended
					}

					$posted_attributes[ $attribute_key ] = $value;
				}
			}

			// Merge variation attributes and posted attributes.
			$posted_and_variation_attributes = array_merge( $variation_attributes, $posted_attributes );

			// If no variation ID is set, attempt to get a variation ID from posted attributes.
			if ( empty( $variation_id ) ) {
				$data_store   = WC_Data_Store::load( 'product' );
				$variation_id = $data_store->find_matching_product_variation( $adding_to_cart, $posted_attributes );
			}

			// Do we have a variation ID?
			if ( empty( $variation_id ) ) {
				throw new Exception( __( 'Please choose product options…', 'woocommerce' ) );
			}

			// Check the data we have is valid.
			$variation_data = wc_get_product_variation_attributes( $variation_id );

			foreach ( $adding_to_cart->get_attributes() as $attribute ) {
				if ( ! $attribute['is_variation'] ) {
					continue;
				}

				// Get valid value from variation data.
				$attribute_key = 'attribute_' . sanitize_title( $attribute['name'] );
				$valid_value   = isset( $variation_data[ $attribute_key ] ) ? $variation_data[ $attribute_key ] : '';

				/**
				 * If the attribute value was posted, check if it's valid.
				 *
				 * If no attribute was posted, only error if the variation has an 'any' attribute which requires a value.
				 */
				if ( isset( $posted_and_variation_attributes[ $attribute_key ] ) ) {
					$value = $posted_and_variation_attributes[ $attribute_key ];

					// Allow if valid or show error.
					if ( $valid_value === $value ) {
						$variations[ $attribute_key ] = $value;
					} elseif ( '' === $valid_value && in_array( $value, $attribute->get_slugs(), true ) ) {
						// If valid values are empty, this is an 'any' variation so get all possible values.
						$variations[ $attribute_key ] = $value;
					} else {
						/* translators: %s: Attribute name. */
						throw new Exception( sprintf( __( 'Invalid value posted for %s', 'woocommerce' ), wc_attribute_label( $attribute['name'] ) ) );
					}
				} elseif ( '' === $valid_value ) {
					$missing_attributes[] = wc_attribute_label( $attribute['name'] );
				}
			}
			if ( ! empty( $missing_attributes ) ) {
				/* translators: %s: Attribute name. */
				throw new Exception( sprintf( _n( '%s is a required field', '%s are required fields', count( $missing_attributes ), 'woocommerce' ), wc_format_list_of_items( $missing_attributes ) ) );
			}
		} catch ( Exception $e ) {
			wc_add_notice( $e->getMessage(), 'error' );
			return false;
		}

		$passed_validation = apply_filters( 'woocommerce_add_to_cart_validation', true, $product_id, $quantity, $variation_id, $variations );

		if ( $passed_validation && false !== WC()->cart->add_to_cart( $product_id, $quantity, $variation_id, $variations ) ) {
			wc_add_to_cart_message( array( $product_id => $quantity ), true );
			return true;
		}

		return false;
	}