It is unlikely that you find a money changer still open around 11pm at the airport.
However, there are ATMs that you can withdraw from at the airport which are online 24 hours.
Nevertheless, it is best to have some small amount of pesos ($20 to $30 dollars worth) as backup for your taxi fare to get you to a money changer in Mabini Street, Metro Manila.
There, the money changers are open until the wee hours of the morning. Some are even open 24/7.
