Rule 107.4f

Phyrexian mana symbols are colored mana symbols: {W/P} is white, {U/P} is blue, {B/P} is black, {R/P} is red, and {G/P} is green. A Phyrexian mana symbol represents a cost that can be paid either with one mana of its color or by paying 2 life. There are also ten hybrid Phyrexian mana symbols. A hybrid Phyrexian mana symbol represents a cost that can be paid with one mana of either of its component colors or by paying 2 life. A hybrid Phyrexian mana symbol is both of its component colors. Example: {W/P}{W/P} can be paid by spending {W}{W}, by spending {W} and paying 2 life, or by paying 4 life.