Do Android/iPhone Apps use AJAX to interact with the backend? If yes, is this common? Or do most apps use a different method for fetching database information. And if so, what other methods are there? Are server-side languages ever involved, and if so, is that more common to see with app development?
The apps that I have written back-end code for (both iPhone and Android) had REST APIs: the app made simple HTTP requests to retrieve XML data.
The server-side was C#/ASP.NET, with .ashx generic handlers that parsed the parameters, did the necessary database interaction, and serialized the response as XML. You could of course use any server-side technology: even considering only .NET, ASP.NET MVC is probably a better solution, or you could even use WCF I believe.
yes , apps can interact with Database by means of webservices(REST or SOAP) in which it can be designed with any server side languagelike php , java or .net etc. we primarily use php for backend support , Say for Example - a news website needs a mobile app so all the web php links will be provided as REST API's in json / xml format to display in the mobile.