Is it ok to use iPhone while it's charging?

Or more specifically, is it healthier to play games through a wall charger or right from the battery?

I have an iPhone 4s

Actually if you often do this, it will not be good for your battery.

I have done this but, I was not playing, I was just texting and doing some sort of stuff with my IPhone while it is still charging. Aside from the extreme heat that it produces, I can also observe that the battery life of my phone becomes smaller.

:( Gotta buy a new batt for me.

No it might actually break your iphones battery, its loosing energy and gaining at the same time, your iphone mught foget what a full charge is and nevr charege past 75%

I have done this meany times while talking on the phone, never had an issue and my battery is still great after 2 years.