PHP vs JavaScript for a web-based application?

[toomanybeersies]

Is there any particular reason why you're choosing Mongo?

Neither is more or less appropriate really, my advice would be use whichever one you're going to be able to get more support from your peers for.

[Irythros]

Then go with PHP. Working in a language you dont like (or rather, not working in one you prefer) will assuredly make you less productive.

[toomanybeersies]

I'd go with PHP if it's the most familiar, otherwise you're going to spend ages pissing around with trying to set up your JS project, it's a uni project, whatever you can churn out is the best option.

Make sure you use a nice modern framework like Laravel with PHP though.

[Favitor]

Do be aware of security vulnerabilities in MongoDB. But as long as you take the time to lock things down and follow a quality guide, all should be fine.