Iphone shows charging symbol in red but do not turns on?

Hye i have an iphone 3g bought it used from someone 1 month ago and now its charging but not turning on… I have left it charging all night but nothing happen… Tried different cable but nothing happen… I have performed a hard reset also nothing happen… What should i do please help

If it is dead, it will not turn on for a while, until the battery has reached atleast 5 percent. Leave it plugged in un disturbed for an hour, then hold the button at the top down until you see the apple logo. If that doesn't work, hold the home and sleep button down until the iPhone shuts off completely, then let go of the home button, but continue to hold down sleep until it turns on. If this doesn't work, call apple