My iPhone will Not turn back on?

My iPhone died, so I went to plug it into the charger.i'm charging & charging it and it still won't come on. Right now the phone just has the apple logo with the black screen. It has been that way for about 30 minutes or longer. It does this sometimes, but never this long. Any reasons why? Or a way I can get it to turn on?

Press and hold the home and lock buttons for a while and it should reboot

You press the POWER button on your iPhone - and nothing happens. Usually, this can be resolved easily. Either your battery has run down, or iOS has "crashed" and needs to be rebooted. On rare occasion the firmware has been corrupted, but let's save that for last. The following steps will usually get your phone working again in a few seconds:

1.Unless you are absolutely certain that there's plenty of charge left on the battery, connect the phone to a wall charger for at least 15 minutes. If it was just a low battery the phone will come on by itself. If it doesn't go to step 2.
2. Hold the HOME and POWER (aka SLEEP) at the same time. An Apple logo should appear in 10 - 20 seconds. Relase both buttons, wait about a minute, and your phone should be back to normal.