I am beginner in programming. I know C/C++ now I want to learn a new language and I am confused which language should I learn first PHP or Dot Net.
Please guide me !!

You shouldn't be categorizing languages in terms of Good or Bad.
Each language has it's strength and weaknesses. Some are better for a particular kind of project than the other.
If I'm just learning a programming language just to add to my knowledge, I would be thinking more of how useful it would be to me with my environment put into consideration. Such considerations would include how popular is the language, how much support is available for the language, etc. But considering the two languages you have in mind, both worth having knowledge of. I'm not sure which to advice you to start with. If you have an important project you want to work on soon, that may be a better consideration for arriving at your decision. However, PHP seems to have gained more popularity in Nigeria especially when considering web applications, but .NET is a more robust language. Google more about he languages then make your choice.