I was browsing MNL's website and found the information to be lacking and confusing regarding the departure tax and connecting flights.
"Under Presidential Decree (PD) No. 1183, as amended by PD 1205, Batas Pambansa (BP) 38 and Executive Order (EO) 283, Filipinos and other nationals travelling to other countries are required to pay travel tax before departure from the Philippines.
Who must pay travel tax
Permanent resident aliens
Non-resident aliens who stayed in the Philippines for more than one (1) year.
Who are exempted
Filipino overseas contract workers
Filipino permanent residents abroad whose stay in the Philippines is less than one year
Infants (2 years old and below)
Foreign diplomatic representatives
Employees of the UN and its agencies
US military personnel
International carrier crew
Philippine foreign service personnel assigned abroad and their dependents
Philippine Government employees on official travel (excluding Government-owned and controlled corporations)
Grantees of foreign Government funded trips
Students with approved scholarships by appropriate Government agency
Personnel of Philippine offices of multinational corporations not engaged in business in the Philippines and their dependents."
It says nothing about connecting pax.