PHP has some advantages. It's easier to get started with. It runs faster than Node (PHP 7 at least). It is under constant new development, lots of new features including strict types, and doesn't depend on upstream features like Node.js does (whatever Google adds to v8).
There are downsides too, with Node you get the same language on both front-end and backend, and some nice tools that tie into that like React server side rendering. Npm and Yarn are nicer than Composer IMO.
Both have large communities, lots of packages, libraries and tutorials available but PHP is older and has many bad old tutorials out there to beware of.
If you learn PHP you're probably also going to have to know JS for frontend work if you do any of that, and it's always nice to know more than one language. OOP PHP is very much like Java so it's easy to pick up Java if you've worked with PHP.
Overall, both are good.