Ask HN: Building a webapp to last the next 20 year. What would you use?

I'm strating a small little personal project. Normally I use them as an excuse to learn some new technology since their success or failure is not really important. But for this particular project I'm thinking on how to build something that last. Suddently this makes me think of using a very traditional stack with php and mysql, not event sure If I should throw laravel into the bucket or having event a more decoupled structure where I can replace modules in case they are abandoned. What are your thoughts in choosing a conservationist stack?