php session destroyed in android application

Question

I am building a login application in android in which i am hitting a url(with username and password) upto that part it works fine but after that whenever I am hitting a url(once the user is authenticated) , it return nothing(i.e. a error message like please login first). However it works fine in very similar iphone app and on browser.

I could not understand that what is the actual problem. Is there any problem on server side(i.e. in php coding ) or there is something wrong with android app. We cant actually blame the server side coding because it works fine for same iphone app and on browser.

Any idea or help will be highly appreciated. Thanks.