What is your preference - .Net, PHP or Java?

I am coming across very open requirements when it comes to preferred web platforms.

I welcome your input to see what are your preferences.

A few people mentioned Ruby / Ruby on Rails as a potential technology for web applications. Groovy is also a strong contender for shops that lean toward Java. For the last seven years I've been involved with a lot of web projects that use Adobe's ColdFusion markup / scripting language. It compiles to Java bytecode and runs in any Servlet container - and therefore has very strong integration with Java. It also has a large library of built-in functionality tailored for the enterprise, such as PDF manipulation, JMS support, automatic SOAP web services support for components, integration with SMS and so on.

It's also worth considering that these days the requirements placed on web applications are increasingly sophisticated and user interfaces need to support more than just simply data entry and table-based display. AJAX gets you part of the way there but it takes a lot of development time and it's hard to maintain cross-browser compatibility. Adobe has done a lot of work on the Flash Player over the years and their Flex tooling is quite remarkable with the XML-based "MXML" UI layout language and the ECMAScript-based "ActionScript" programming language.

Whilst some may rail against a proprietary technology stack (although it doesn't appear to be an issue for people who prefer .NET / Microsoft), Adobe has also worked hard in the Open Source arena, donating the core of the Flash Player engine to the Mozilla project (as Tamarin) and providing the Flex 3 SDK as open source, as well as the server-side messaging engine BlazeDS which provides Flex's bridge to Java (or Groovy). The Adobe Integrated Runtime (AIR) allows you to take web applications to the desktop as well to provide occasionally connected online/offline capability. As others have noted, requirements are the key driver, along with any client considerations of existing technology or preference. I was just surprised that no one had mentioned the web tooling of one of the other largest software companies out there...

Disclaimer: I was the senior architect for Macromedia's IT division for several years and remained with Adobe for a year after their acquisition of Macromedia so I am somewhat of an evangelist for their technologies (and just came back from their annual MAX conference in San Francisco where they showcased their current and future technology offerings).