My iPhone won't charge, even though it's giving me the charging logo on the screen

So my iPhone died, and I put it on charge, and it gave the battery image on the screen to say it was charging, but even after a day of non-stop charging it won't come back on. I've trying doing a reset (where you hold the home button and lock screen button) while it's charging, this causes it to quickly display the image that shows that it needs charging before then changing back to the image that shows it is being charged. Doing it while it's not charging just brings up the screen that says it needs charging. What should I do? My charger definitely works because it charges my iPad with no issues. Thanks in advance!

EDIT: forgot to mention, it's an iPhone 5s I've had for about 15 months.