Php stands for “people hiding ponies” afaik. Basically it’s for artists who want to remain anonymous but have a tag— or artists who do want or don’t mind to keep their art up but don’t want it associating it with their current name.
March 23, 2021: I would like to sadly say that gray–day had just deactivated his account on deviantart.
I don’t know why it happened but everything that was there is now gone forever.
I’m somewhat concerned that something bad must’ve happened in his life.
It’s a crying shame to see that an archive full of natural talent has just been lost and that its owner, a distinguished and veteran artist, has decided to disappear without saying anything and leaving anything behind.
I hope that someone can reach out to him and ask what had happened that caused him to do this.
So as far as I can tell, anything by Ponykillerx not uploaded in preview size in this 2017 EQD post is gone for good. I don’t think they had any other accounts other than Tumblr and DA which are both deactivated…