Number of people inside a store = ?

Hi all
Do you have an idea how I can check the number of people that go inside and go outside a single door store? I need to know how many people are inside.
Thanks

That's been done on this forum a thousand times over.

If you have an in door and an out door and people can't go backwards then it is as simple as a break beam sensor on each door.

If it is a two way door then you need two sensors one a little further in than the other. If someone breaks the first sensor then the second then they're coming in. If they trip them in the reverse order then they're going out. All you have to do is keep up with a flag indicating whether or not you've already tripped one sensor and therefore have someone in the middle.

You need to use Two IR Proximity sensors at horizontal distance d. So, if sensor A cuts first then that means person is entering and if sensor B cuts first then person is leaving.

You can also use Ultrasonic sensor HC-SR04 instead of IR sensors.