Fun for UD :-)

ud-custom-redirect

<?php
/*
 * Plugin Name: Brad Gives to Usability Dynamics
 * Plugin URI: https://bradgriffin.me
 * Description: Look at your pageflow. After a user adds anything Invoice related to my cart, redirect the user to another Invoice related product. Same concept with the Property products. Almost immediately, you're total per transaction amount will go up #whoop!  
 * Author: Brad Griffin
 * Author URI: https://bradgriffin.me 
 * Version: 1.0
 * License: GPL 2.0
 * Text Domain: woocommerce
*/

//* Add/Display Fields
add_action( 'woocommerce_product_options_general_product_data', 'bkg_woo_add_custom_general_fields' );
function bkg_woo_add_custom_general_fields() {

	global $post_id, $woocommerce, $post;

	echo '<div class="options_group">';

	woocommerce_wp_text_input(

		array(
			'id'          => '_bkg_woo_product_custom_redirect_url',
			'label'       => __( 'Redirect on Add to Cart', 'woocommerce' ),
			'placeholder' => 'http://',
			'desc_tip'    => 'true',
			'description' => __( 'Enter a URL to redirect the user to after this product is added to the cart.', 'woocommerce' ) ,
			'value' => get_post_meta( $post_id, '_bkg_woo_product_custom_redirect_url', true )
		)

	);

	echo '</div>';

}

//* Save Fields
add_action( 'woocommerce_process_product_meta',  'bkg_woo_add_custom_general_fields_save' );
function bkg_woo_add_custom_general_fields_save( $post_id ){

	$bkg_woo_redirect_url = $_POST['_bkg_woo_product_custom_redirect_url'];

	if ( ! empty( $bkg_woo_redirect_url ) ) {

		update_post_meta( $post_id, '_bkg_woo_product_custom_redirect_url', esc_url( $bkg_woo_redirect_url ) );

	}

}

//* Redirect to URL
add_filter( 'woocommerce_add_to_cart_redirect', 'bkg_redirect_to_url' );
function bkg_redirect_to_url() {

	global $woocommerce, $post;

	$product_id = apply_filters( 'woocommerce_add_to_cart_product_id', absint( $_REQUEST['add-to-cart'] ) );

	$bkg_woo_redirect_url = get_post_meta( $product_id, '_bkg_woo_product_custom_redirect_url', true );

	if ( ! empty( $bkg_woo_redirect_url ) ) {

		wp_redirect( esc_url( $bkg_woo_redirect_url ) ); exit;

	}

}