PhiCorp was a company that produced painkillers without narcotic side effects. Despite a clean public image, it hid a dirty underbelly of illegal activity in the wake of a new world order where PhiCorp could exploit the Miracle for monetary gains.
History
In return for his protection, one of their representatives, Jilly Kitzinger, recruited Oswald Danes to speak in favour of allowing all drugs to be available without prescription. Rex Matheson theorised that this would increase their profit a thousand fold.
Jack Harkness, Gwen Cooper and Rex infiltrated a PhiCorp warehouse. They discovered a massive stockpile of drugs, leading them to believe the company had prior knowledge of Miracle Day. Jack said it was "bigger on the inside." (TV: Dead of Night)
Upon interrogating COO Stuart Owens, Jack Harkness learned that, while PhiCorp managed to profit off the Miracle, they were as much in the dark as anyone else. Owens had his own investigators trying to uncover the truth behind the Miracle, and how PhiCorp was being used in it, but the only investigator who had apparently learned anything chose to jump from a tall building after he discovered something that drove him to suicide. (TV: The Middle Men, The Gathering)
Jack Harkness then found out the link between PhiCorp and the Three Families after realising the PhiCorp logo represented the Blessing. (TV: The Gathering)