As in phala फल - fruit (effect)
頗字門，入諸法遍不可得故
The syllable PHA is a gateway because one enters that all dharmas fulfillment cannot be attained.
Kuamrajiva
入頗字門，悟一切法遍滿果報不可得故
Entering the gateway of the syllable PHA, one realizes that the fulfillment of the fruit of all dharmas cannot be attained.
Xuanzang
頗字門一切法不堅如聚沫故
The syllable PHA is a gateway because all dharmas are insubstantial like foam (pheṇa)
Amoghavajra
PHA because no fruit (phala) is apprehended.
Conze
The syllable PHA [means] all mental phenomena are openings because of the non-attaining of fruit (phala).
Jayarava