I don't think there is something in php that you can't do in node and vice versa. So choose the one you are comfortable with.
But I guess the way they handle requests are different. For instance node handles requests concurrently whereas php spawns a separate instance for each connection.
Also for php you will need apache or nginx.
Node has npm, php has its own libraries/utilities etc. Php 7 has also huge performance benefits compared to 5/6 etc.
Personally, although my main language is javascript and I work with node, I like php's syntax better, its just sugar. I also have strange feelings having javascript on server side, maybe it's just that I'm a salty neckbeard.
There is no right or wrong here. Look at both languages, play with them a little, choose the one that feels right for you.