向网站添加XML反馈功能

Few years back I made a university website using PHP where notices are uploaded and students can see it.Now they want me to develop an android application which I can use to get notices from the website using XML parsing.

That is,the website should have dual functionality -It can be accessed by a PC (like normally we do) as well as it can be accessed by the app.I can develop the android app.That part is OK.But the problems are on the source-side(server-side).I have following questions :-

1)Do I have to buy a separate url for xml responses and share the old database?

2)If not , then how can I add XML feed functionality and how will I identify the client whether it is a PC or the app(a guidance).

The website screenshot

Any good tutorial will be appreciated.

Do I have to buy a separate url for xml responses

No.

and share the old database?

Presumably you want to use the same database. If you want different content (as well as difference presentation of that content) then you should have it on different URLs.

If not , then how can I add XML feed functionality

Pick your favourite PHP XML library.

and how will I identify the client whether it is a PC or the app(a guidance).

Don't try to identify what the client is. Identify what sort of data it wants. Use the HTTP Accept header.