He said he was thankful for the help he and the others received from the U.S. Embassy in Cairo, administrators at American University in Cairo, and attorneys in Egypt and the U.S.
"I'm just so thankful to be back, to be in Philadelphia right now," he said.
Porter, Derrik Sweeney, 19, and Luke Gates, 21 - students at American University - were arrested Wednesday, accused of throwing Molotov cocktails at security forces from a roof of a university building.
Protests have been raging in Tahrir Square since Nov. 19 in anticipation of parliamentary elections scheduled to begin today.
At least one member of the trio disputed the version presented by authorities.
Sweeney, a Georgetown University student, said Saturday that he and his fellow students "never did anything to hurt anyone," were never on the roof and never handled or threw explosives.
Sweeney, the last of the three to arrive home late Saturday, recounted how tear gas clouded Cairo's streets and how he heard armored vehicles and what sounded like shots being fired just before his arrest.
In a telephone interview with the Associated Press, Sweeney said he and the others were told by a group the night of their arrest that they would be led "to a safe place" amid the chaos engulfing the nearby square.
Next, he said, they found themselves being taken into custody, hit and forced to lie for about six hours in a near-fetal position in the dark with their hands behind their backs.
The worst, he said, was when they were threatened with guns.
"They said if we moved at all, even an inch, they would shoot us. They were behind us with guns," Sweeney said in the brief interview.