magnitude in a table?

I am trying too make a function which will check for player that is closest to the zombie. The script is inside the zombie but it returns nil for every player without player 1.

local torso = script.Parent.Torso 

function getClose()
	local ptorso = game.Players:GetChildren()
	for i = 1, #ptorso do
		local ptab = {
			(torso.Position-ptorso[i].Character.Torso.Position).magnitude;
		}
		print(ptorso[i].Name,ptab[i])

	end
end