Philippines has finally realized who is foe and who is friend.

http://www.straitstimes.com/asia/se-asia/us-philippines-to-end-military-exercise-a-day-early

Philippines terminated its joint military exercise early with USA because Duterte had realized that the exercise was not beneficial to Philippines.  The joint military exercise was performed with all USA weapons and technologies and USA would take back all its equipment after the exercise leaving Philippines operational readiness ineffective without USA equipment.

Therefore, if China and Philippines were to wage a war against each other, Philippines would be wiped out fast and furious without USA equipment.  USA would not supply all the equipment that Philippines needed to win the war at the expense of USA.  How did Duterte come to this conclusion? He took the leaf out of Crimea to form this conclusion because USA did nothing to help Crimea when Russia annexed it.

Philippines also realized that South China Sea became an issue after USA decided to get involved iand USA was the real troublemaker wherever it went.  Therefore, Duterte decided to turn the situation around by getting cosy with China for the greater good.