Why is my iphone doing this ?

my iphone ran out of battery, and when i plug it in . its just stuck on a battery with a little red line in and a volt/charger icon underneith.. but its not atchully doing anything.. or charging its jus been stuck like it for days, and when i unplug it is says to plug it back in.. ?? realy confused. also i have reset itunes . like reanstalled it. but its still doing it