A lot of people may not know that the 30 day visa free stay does not include the day of arrival. What I used to do was plan to leave after midnight and go thru immigration before midnight on my last day, that way I got the first day and the last day without fear of overstaying. Of course if my flight were to get canceled then I would need to extend by getting a visa.
The reckoning of the thirty days (30) begins on the day after arrival in the Philippines. This visa-free stay allows for regular tourism and business meetings. http://www.philippineconsulate.com.au/visa/the-philippine-visa.html