Sharing auth between applications on the same domain?

I am trying to run two applications on the same domain. A config file decides which application handles the request depending on the url.

The applications are using the same database and have to use the same authentication.

For now, the applications are both built with PHP (Laravel and Kohana), but I am looking for a generic solution that could also work if one of them is going to be swapped with for example VueJS.

This issue is quite similar and suggests to work with JWT.

I am not sure if this is the way to go and this means quite some changes in both the applications. I really need a solution so if this requires the least adjustment then that is the answer.

Is JWT the way to go or are there better solutions?