I want to develop an iPhone native app, that sync with a remote DB.Is it possible to develop this application using PhoneGap.If I use PhoneGap, how do I get data from an externa
wm_eddie is correct.
Also, I wanted to comment on your "I want to build a native iPhone app" quote. Applications written for PhoneGap are not native apps. While they can be made to look, and for the most part, act like native apps, a better analogy is to think of them as pre-packaged, locally installed, web apps that can, using the PhoneGap api's, get access to a limited subset of native functionality. Notably, this functionality consists of sensors (accelerometer, gps, etc) and camera operation among others.
This may have no bearing on your usage, but just wanted to clarify the point... ;)
(PhoneGap is still a very nice tool, and I'm using it in some of my projects. However, if you need a fully native app, except for the JS which must be interpreted at run time, but is pre-compiled using mostly 1-1 language dependent symbolism, then I'd recommend Titanium which I'm leveraging as well. Both nice tools, but they deliver distinctly different products with different benefits and disadvantages. It's a matter of determining the requirements of your end-product and then choosing the platform that makes the most sense.)