I want develop a mobile app (for Android) for indoor navigation on my university. Which a programming language is the best for that? Can I use for example JavaScript for frontend and PHP for backend?
Thanks :)
DISCLAIMER: I work for an indoor navigation company.
There is no programming language that is "better" for indoor navigation. If you are comfortable with javascript, I would say use that rather than learning a new language altogether. I say that because developing an "indoor navigation" application can be a pretty big undertaking without any third party platforms that do a lot of the heavy lifting for you (Map Rendering, Map Management, Wayfinding Logic, etc). There is also a lot of new terminology that you may need to learn in order to even begin searching for the right answers.
A few things you may want to look into are:
Map Digitizing, You'll need find an up to date map somehow. This is a lot harder than it sounds. Further, once you find it you'll need to convert it into a format that is both lightweight & accurate. PNG, SVG, GeoJSON, KML, WKT are some formats to look at. GeoJSON might be your best bet.
Map Rendering, There are a lot of great open source rendering engines you can use that have great documentation. There are also a lot of paid & enterprise ones.
Wayfinding, This is drawing a path from one point, typically the users location, to another, the end destination. Here is an example of how some wayfinding algorithms work: https://qiao.github.io/PathFinding.js/visual/
Map Management, Indoor spaces change much more frequently than outdoor. Think about your example, a University will have different classes & schedules each semester- this will need to be managed in a CMS somehow and by someone.
That isn't everything, but should be enough to get you started.