The company I work for has two websites. Website-1 is the public website with a product catalogue and Website-2 is a secure website (requires login) where our customers can buy products. The problem is Website-1 and Website-2 don't exchange information. For example, there can be a personalized offer on Website-1 for a customer but they're required to login two Website-2 to buy the product. However, when they login to Website-2 the customer is required to navigate the website to find this product. This is a bad customer experience and our customers can't find the product. When the customer logs in to Website-2 I would like a Call To Action to pop-up immediately so they can buy the product and there's no navigation. How do I explain this in technical terms to the developer team? - that Website-1 needs to send info to Website-2
Since people are commenting on your question and you seems to have your concerns to maintain two different sites. Thus, I will try to answer your question which you have asked.
On the contrary, I do believe its not worth to maintain this favoritism for new and old customers. Instead having a reliable portal for both would be an ideal solution. Thus, saving you server/development/maintenance cost and giving you leverage to work on new cool/requested feature.
Solution to your concern Issue :-)
1) You can have a single/common Database, thus both sites have consistent and up-to-date data. Eg: If a last item of particular product is just bought on on Website-1, then it should not be remain listed for sale on Website-2. -- In simple words, better to have a common Backend for two different Frontend Application. Almost all the web applications (who also have a mobile application) follow similar regards. Such as; facebook/twitter both posses same database/backend server but for the clients it variates, some use online in web browser and others on their mobile devices.
2) Your requirement of passing parameter of Website-1 to Website-2 can easily be handled with custom rich URLS. Lets take the url of this question of yours
First part: says navigate to webmaster.stackexchange.com
Second and Third part: says that its a question with an identifier 118504
Fourth part: is a short compressed text of your provided title to maintain good SEO.
Similarly, you could have
**Buy Now Button**or
**Proceed to Payment**on your Website-1 Product, which should be redirecting to some url like this
www.website-2.com/shirt/123456/blue/small/newyearsale. So when you navigate to this URL you can easily interpret this URL with your controller on Website-2 and can understand that this user is being redirected from Website-1 and would like to purchase Blue Small sized Shirt with ID: 123456 available on discount for NewYear.
Since, now you know why user landed to your site; you should now show Button to
**PAY HERE** or
**CONFIRM YOUR ORDER** and proceed with the transaction on your secured Website-2.
Hope this helps. Cheer!