is it ok if you forgot to turn off the wifi and connected to the internet the whole night

Staying connected to WIFI all night is not a problem. Something else was draining your battery.

Restart your device by holding the home and power button until the Apple logo appears. This may resolve the issue. It did on my phone when the battery was discharging at a higher than normal rate.

Just because wifi is on and connected to your wireless network does not mean there is any traffic at all. There would only actually be any active network activity if you had an app or process that needed access to the network. For example, iCloud backups are set to normally occur when the device is plugged in, the screen locked in sleep mode, and an active wifi connection is available. For many people that happens overnight, when they are sleeping and their iPhone is left to charge overnight for the next days use.

There honestly should never be a need to ever turn off wifi, so as raymond says, something must have been actively running over-night. Did you leave any location-based app running in the background? What other background apps do you have enabled? How many items are in your notifications settings? Do you use push email or automatic fetch that might have been actively getting data overnight?

provoked wrote:

Is it ok if you forgot to turn off the wifi of your iphone and connected to the internet the whole night and it become warm , because i forgot to turn off my wifi and it connected to the internet the whole night and when i woke up its now 7% but last night before i go to sleep its 60% is it normal?

If your phone was not plugged in, when the screen went dark, the WiFi connection would have dropped. The phone would have been connecting to the network by cellular data as required. So, even though WiFi was still enabled (I never turn mine off), the phone was not connected to WiFi or to the internet all night.