Some people (like me) tend to treat night VFR flight basically the same as IFR flight. You can't see the clouds, you can't see the terrain, you can get all kinds of different illusions, navigation is completely different, some methods of judging flare height that work at day won't work at night, etc.
And on top of that, as Pace says, you should get some instrument training before considering night qualification (though I think it's rating now under Part FCL), because at night you can't control attitude with just looking outside, since most times you don't have a clear horizon - you have to use the attitude indicator. And looking at the attitude indicator correctly is not something you can become proficient in that quick.
While you can (by law) get a night qualification/rating during your PPL training, anyone with just a tiny bit of common sense would highly recommend against doing it.