It is possible that the reason for the hot voice of the iPhone charging is. It's caused by charging while playing. Some mobile phones do not support charging while playing.
This will cause the internal pressure of the phone to be too high, resulting in excessive temperature.
It could be or it could be an expansion of the charging current. More than cell phones. Can meet the limit of current.
The power chip can't take it. Which causes the phone to burn.
The third is that there may be a problem with the charging head and the charging cable. Try a new charger. The last one is the battery.
If you've tried all of the above and it's still hot. That's mostly a battery problem. Cell phone batteries have a lifespan.
Need to be replaced regularly. If it is not replaced for a long time, it will cause the battery to bulge. You'll have to wait. It could even explode.