check for players who exists from ents.findinsphere

Garry's Mod coding
#1

how could i check for all players that exits from a sphere?

#2 

local SphereCenter = place you want sphere to be
local SphereRadius = distance you want in Source units

function PlayerLeftSphere(ply)
	print(ply:Nick() .. " has left the sphere!")
end

function CheckSphere()
	iterate through players
		local pos = player's position
		
		if (distance between SphereCenter and pos > SphereRadius) then
			if (ply.InSphere) then
				PlayerLeftSphere(ply)
			end
			
			ply.InSphere = false
		else
			ply.InSphere = true
		end
	end
end
hook.Add("Think", "ply in sphere", CheckSphere)
#3

that’s really clever, thank you