do i need transit visa for my return date back to my country?

hi , im a philippine passport holder and i will go to mexico, with connecting flight to shanghai pvg. i already have my onward tickets and will not stay for more than 24 hours in the airport. i understand that with the given situation i do not need transit visa.
my question is, when i go back after a month from mexico to shanghai china (my transit country) back to the philippines, is the process still the same? i already have my tickets again and the hours i will stay will nto exceed 24 hours. am i still exempted from obtaining a transit visa?
please help :S asap....