PHP Working Sets are groups of PHP resources which allow you to view or apply actions to a group of pre-defined elements. Workings Sets group elements under one title so that they can be easily selected when viewing resources or carrying out actions. Elements included in a PHP Working Set can include any PHP project, folder or file.
Selecting the 'Select Working Set' option in the Project Explorer view's context menu allows you to choose specific Working Sets (i.e. group(s) of projects/files) to be displayed in the view.
Projects/files not in the selected Working Set will not be displayed in the view.
If you have not created PHP Working Sets, see Creating PHP Working Sets for more information.