What cryptocurrency is measured in photons?

The Photon cryptocurrency, abbreviated as PHO, was released in February 2014 is the cryptocurrency measured in “photons”. (Note that the word “photon” is also the name for a quantum of electromagnetic radiation, which has nothing to do with cryptocurrency. But it is a cool name and that is probably why PHO chose its name.) The original intent of the PHO developers was building a blockchain-based economic infrastructure meant for the video games, unlike most other cryptocurrencies. PHO is an in-game currency for payments between game users or making purchases from the game.