<p>I am doing 2nd year computer science and we have a software engineering group project. There are 5 people in the group and we would like to build a web application in php. Please suggest some ideas for me </p>

How about a
content management system
?
This allows you to show off every part of your web development skill and it shouldn't be hard to do with a 5 person team. CMSs often include file uploads, file management and on-line text editors (something like TinyMCE).
They're actually quite fun to develop and when the system is completed it has a great "wow" factor. Especially when you show people how you can edit the contents of your website on-line.