My Iphone4 went dead and won't turn back on inspite of charging it for whole night. Any idea?

Try holding down the power and home button together for 10 to 15 seconds or until you see the apple logo.

Try the suggestions in this Apple document -> Troubleshooting iPhone hardware

Will not turn on, or will not turn on unless connected to power

1. Verify that the Sleep/Wake button functions. If it does not function, inspect it for signs of damage. If the button is damaged or is not functioning when pressed, seek service.
2. Check if the Liquid Contact Indicator (LCI) in the headset jack or dock connector is activated or there are signs of corrosion or debris. Learn more about LCIs.
3. Connect the iPhone to the iPhone's USB power adapter and let it charge for at least 15 minutes.
4. After at least 15 minutes, if:
   • The home screen appears: The iPhone should be working. Continue charging it until it is completely charged and you see this battery icon in the upper-right corner of the screen . Then unplug the phone from power. If it immediately turns off, seek service.
   • The low-battery image appears, even after the phone has charged for at least 20 minutes: See "iPhone displays the low-battery image and is unresponsive" symptom in this article.
   • If something other than the Home screen or Low Battery screen appears on the display, continue with this article for further troubleshooting steps.
5. If the iPhone did not turn on, try resetting it while connected to the iPhone USB power adapter. To reset, press and hold the Sleep/Wake button and the Home button at the same time for at least ten seconds, until either the Apple logo or the battery symbol appears.
   • If the display turns on, go to step 4.
   • If the display remains black, go to next step.
6. Restore the iPhone. Connect the iPhone to a computer and open iTunes. If iTunes recognizes the iPhone and indicates that it is in recovery mode, attempt to restore the iPhone. If the iPhone doesn't appear in iTunes or if you have difficulties in restoring the iPhone, see this article for further assistance.
7. If restoring the iPhone resolved the issue, go to step 4. If restoring the iPhone did not solve the issue, seek service.

If that doesn't work, have a Genius take a look at it.

same with me

I had a similar problem and tried the 30-second reset, didn't work. Have sent it to a local Apple service center in Mumbai, India. Hope they resolve the problem. Quite surprised that this seems to be too common a problem! Almost felt like going back to my trusty old Nokia!

My phone has the same

Problem

Thanks for the tip. It sorted the problem for me. 🙂

worked 100% Tks