How did the apostle Philip die?

A:

Apart from James and perhaps Judas, we do not know when or even how any of the apostles died, and no reputable source describing Philip's death has been found. However, in the centuries that followed, Christians sought to portray all the apostles as incredibly brave men who sufferred great hardships and martyrdom for their faith.

One of two main Christian traditions, taken from the Acts of Phillip, is that Phillip was crucified because he converted the wife of the proconsul of the city of Hierapolis. To make the crucifixion seem more special, it seems that he and Bartholomew was crucified upside down. Even in that position, Phillip continued to preach to the crowd that had assembled. Acts of Phillip was written anonymously, probably in the fourth century, and this story only appears in its appendix, suggesting quite late authorship of the passage.

Another Christian tradition is that Phillip was martyred by beheading.
 

A:

St. Philip was a martyr but how he was killed is not known.