Opening existing project in Eclipse is not as straightforward as in Visual Studio, becuase Eclipse treats project on folder basis, and there is no project file as far as it is concerned, unlike Visual Studio, so one can't click on a project file to open all the files that are located inside a folder.
This creates a problem if your website is never a part of the Eclipse workspace and now you want to work on it in Eclipse.
In order to solve this problem you first have to bring in the project into your Eclipse workspace.
Here are the step-by-step instructions on how to do it.
First, you click on File->New-> PhP Project, Or any other project such as Python or Perl. You will have to manually tell Eclipse that you are going to work on this project by creating a new Eclipse Project in the Explorer.
Then, you have to go to File->Import, and choose the File System option:
Select the directory where your files are located and the input Folder, which is phpTestImport in this case:
Click Finish, and the file is imported!
And now you can do your editing in Eclipse!
Troublesome? I think so.