How to get my iphone to turn back on?

My iphone lock button broke a few days ago and then today it turned itself off and won't turn on it is charged.anyway to turn it on i have tryed plugging it into the computer.

Try spitting near the lock button, the syliva will loosen up the interior near the lock, that will have a good chance of opening again. I had the same problem the other day, my iphone wouldn't charge even after I plugged it into the computer. Micraculously I somehow had a large chunk of spit just throb itself over the lock after wiping it I tried it again, believe or not it worked.

If your lock button is broken, you can call 1-800-MY-APPLE and give the Apple Care Tech Support your serial number. Depending on how old the iPhone is, you may be covered under your one year hardware warranty and be able to get it fixed.

-Otherwise, the steps to turn an iPhone back on are simple.
-While plugged into power:
-Hold the power button, count to seven or until something happens. Let go and let the phone boot up. If no response…
-Hold both the power button and the home button down at the same time, count to seven, then let it boot up if the apple logo appears.

If neither of these work, then you have more issue than just the lock button not working.

You can find information from here-

This is what i found online:

Option 1: Let the phone discharge until it turns off. Then, you can charge it again and it should turn on when it reaches a high enough battery level.

Option 2: If you dare, you can reset the device's network settings which will restart it (but obviously, also clear your network settings).

Option 3: But really, you should take it into an Apple store, so they can deal with the underlying problem of your broken button!

If all else fails and your iPhone is really dead, just sell it online and make an upgrade! There are sites that accepts iPhones (may it be old, used, and broken). I recommend Cashforiphones.com and learn how much will they pay for your broken gadget.