Phoshare reads library data from a XML file that was automatically updated by iPhoto (and Aperture) with information about the content of your library. The amount of information contained in that file was greatly reduced in recent versions of iPhoto (probably for performance reasons - the file got very big for large libraries, and had to be entirely rewritten on every update), which made Phoshare a lot less useful, and lead to my decision to no longer maintain the tool. Photos doesn't export any library information (no XML file at all). To make Phoshare work with it, one would have to reverse engineer Apple's non-published SQLite database schema, and rewrite Phoshare to directly read data from that database.
Not impossible, but not a trivial task either.
Tilman