Not to mention the cost to maintain such advanced equipment and the technology and training needed to handle the equipment. And if one malfunctions cause ur pilots or technicians are careless or you get shot down from a RPG...well too bad....there goes your ONLY advanced aircraft.
You have too many accidents in the PAF anyway. If they can't handle WW2 or Vietnam era let alone maintain them...how can they handle an advanced 21st Century or late 20th century aircraft?
You don't need F-22's or whatever. The US Government also doesn't want you to rely on SOVIET COMMUNIST MADE weapons. They feel your government will turn socialistic as most if not all Asian nations are like or split between on views.
What you need is a massive updated navy and ground force. Not an Air Force. You're people won't really fight nor have the resources to. If invaded it'll take the tenacity and perseverance to wage a 40+ year civil war till the invaders tire out at 10 years. With millions of dead filipinos in the aftermath and women and children brought in as rebel fighters to win.
That is usually the outcome of most defeated militaries. They rely on the people to stage uprisings everywhere.
But don't expect the Philippines to be invaded. It is CHEAPER to just BUY you out with CASH.
You need a stronger ground force and better navy. And manufacture your own weapons and produce your own oil for use.