How to add rewrite rule for product compare page?

Question

I'm trying to create a product compare feature where we can compare three products, Two products must be added while the third is optional.

Trying to use the add_rewrite_rule to create a friendly URL for the product compare page. For example, Something similar to this https://hostadvice.com/tools/web-hosting-comparison/godaddy-vs-hostinger/

To make it work, The following is the what i tried so far, I know this is not the correct one.

add_rewrite_rule( 
    'compare/([^-vs-]*)(?:-vs-)([^-vs-]*)(?:-vs-)([^/]*)?/?',
    'index.php?pagename=compare&compare=$matches[1],$matches[2],$matches[3]',
    'top'
);

desired url structure:

example.com/compare/product1-vs-product2-vs-product3

While the product3 can be optional

It'd be really helpful if someone can correct me on how to make the regex expression work correctly.

Thank you.

Answer 1

Here you go:

compare\/([^-vs-]*)(?:-vs-)([^-vs-]*)(?:-vs-)?([^-vs-]*)?

Remember to escape backslashes (as I have done). I also made your lookups more consistent in their internal logic/structure.

I assumed you wouldn't want a second -vs- if the third product wasn't there, so this is why you now have the second non-capturing group.

Here is a link with the answer in regex: https://regexr.com/3u465 to make things clear. Please let me know if I misunderstood your requirements. :)