Q: Is it true that your iphone charger will only get the right amount of volt for your iphone

The charger auto-switches between the two. You are OK to charge there.

Apple Chargers are rated for use with AC currents between 100 and 240 volts.  This covers pretty much every voltage in the world.

The chargers will automatically adjust for the input voltage when plugged into the socket.

You can plug in the charger in the philippines just fine and use it to charge the iPhone.

The "charger" is actually in the phone.  The white brick you plug into the wall is merely a power supply (takes input from the wall socket and converts it to USB standard output) , and it will accept any standard input voltage (100-240V) -  http://www.apple.com/power-adapters/ Since the output is based on USB standards, it is always 5V.