is there any site providing environment for test php code online?

if you just want to test your php code, you can do it offline, there are a lot of free web server application package that you can install on your computer, such as xampp (apachefriends.org), you can run your code from localhost the same way as if you put it online,

but if you want to test it on a remote server, a bit of google will solve your problem, like OriginalGriff said,

Alternative approach is testing PHP on your own computer. Install Apache (http://www.apache.org/[^]), PHP and PHP module for Apache. This server is lean enough, secure and most used.

There is another approach which is good if you can use Visual Studio. You can use PHP for .NET called Phalanger, see http://en.wikipedia.org/wiki/Phalanger_(compiler)[^]. A plug-in for Visual Studio is also available. Using these tools, you can even use stepwise debugger!

You should remember though that Phalanger is very different from "standard" PHP. If your goal is using "standard" PHP but you want debugging with Phalanger under Visual Studio, develop and debug separate PHP modules and stick to a "standard" sub-set of feature, for example, do not use .NET binding.

—SA