According to information provided by the U.S. consulate, before you can obtain a marriage license to wed in the Philippines, you, the U.S. citizen or resident, must first submit a "Legal Capacity to Contract Marriage" from your embassy. Unfortunately, the U.S. embassy does not feel it can provide this exact document, and will instead give you an “Affidavit In Lieu of Certificate of Legal Capacity to Marry.” Some of the local registrars have been known to refuse to accept this affidavit; you will have to find one who does accept it. Instructions on how to make an appointment to obtain this Affidavit are given on the “U.S. Citizens Services” page of the embassy website.
At a minimum, the U.S. citizen will need to present the documents below – and additional items (such as baptismal and confirmation certificates) if it’s a church rather than a civil wedding:
evidence that any of your past marriages have ended, such as a divorce decree or death certificate
U.S. passport
documentation regarding paternal consent or advice if you are under age 24 (as described below).
You can be legally married in front of a judge, minister, or other person authorized by the Philippines government. If either of you is between the ages of 18 and 21, you must provide written parental consent; and if either is between age 22 and 24, you must show that you have received parental advice. Philippine law does not allow marriages by anyone under 18.
You will need to plan ahead for a ten-day waiting period between the filing of your application for a marriage license and its issuance. The license is good for up to 120 days.
After the ceremony, you will need to wait another ten days before you can obtain a certificate of that marriage for purposes of U.S. immigration.
Note that this process took 20 of the 24 days he was there.