To get a Philippine birth certificate online, go to e-Census website of Philippine National Statistics Office and simply follow the instructions. You can also call (02)737-1111 for your birth certificate to be delivered on your doorstep.
e-Census https://www.ecensus.com.ph/
NSO Birth Certificate Delivery http://nso.citizenservices.com.ph/
You may also visit Batch Request Entry System (BREQS) outlet in municipal/city hall or in a SM business center nearest to you.
Of course, other civil registry documents like marriage certificates, death certificates, and certificates of no marriage (CENOMAR) are also available.