rnaik, u r a hobbyist programmer, right....? ASP/PHP maybe enough for u, but thinking about giants like MS, SUN, IBM is out of ur bounds. see these companies not only have sites which serve lacs of ppl per day but the softwares/tools which have equal number of users. frankly I don't know about PHP, well ASP is outdated as ASP.NET overtook it and ASP had many disadvantages which were taken care of in .NET. I work for Accenture nd I work on .NET.
IMO companies dnt use PHP bcoz its opensource. well I dnt agree with #/bin and u on Java. It is one of the most used and dependable programming language for web applications, and let me remind u its not slow even. In handling thousands of requests per second (yes eg. MS/Yahoo servers get those many requests) Java(MS doesnt use Java) has proved its mettle. while .NET is gradually on rise, and it may be the future (well I m just guessing, not predicting), it has also got same impressing results. moreover .NET applications are sturdier too.