Hi I'm Gordon. A university student studying computer science.
I have worked in internships in the past and has experiece in PHP MVC and Spring MVC(Java).
I suggest using PHP MVC with Twig Template for this project that you are working on.
1. PHP is a server-side language and clients' information is secured
2. MVC (Model-View-Controller) is a good programming model to follow and is easy to maintain and expand the project later on.
3. I see that you would like to make an app. I suggest making a web app which is responsive to the device screen size. Then, you won't have to make 3 separate projects for Android, iOS and a website.
We will be using MySQL, ApacheTomcat, PHP MVC and Twig Templating engine.
Cheers
Gordon