Are we using the right web language for development?

I know this is probably open to opinion but currently my company wants the web application to be written in PHP.

The concern/problem is how the MD has described the view of the application to the development team.

In short he wants to have a lot of grid like controls for data input, multiple floating windows etc. Basically a desktop application in a web format.

I'm concern that PHP is the wrong language and that maybe C#/ASP.Net with all the windows like controls might be a better option.

I've done some searching on PHP and HTML5 controls but with the majority of the requirements I keep ending up with a company called DevExpress which seems to have everything we would need.

Also when I look at controls for this for use with PHP, there's a large choice but a lot of the "good" ones have associated cost and the company want to use open source everything.

I'm seeing the need for a lot of call backs, floating 'popup', dock able controls, excel/spreadsheet data entry etc.

I think we are being pushed down a path where we wouldn't be able to deliver the functionality that they want.

I would be interesting in the community opinions on this, maybe my experience with PHP it limited to standard web sites.

Jim