Trying to give and ID to an entity

[The French Spy]

Hello guys, I'm trying to make a little script and i need to give an ID to an entity. I want the first entity toh ave the ID 1, the second entity the ID 2, so on and so forth.
So i use a variable called VentLastId that I set to 0 when the entity initialize in init.lua

function ENT:Initialize()
    self:SetModel( "models/props_junk/vent001.mdl" )
    self:PhysicsInit( SOLID_VPHYSICS )
    self:SetMoveType( MOVETYPE_VPHYSICS   )
    self:SetSolid( SOLID_VPHYSICS )
    self:SetUseType(SIMPLE_USE)
    VentLastId = 0
    local phys = self:GetPhysicsObject()
    if (phys:IsValid()) then
        phys:Wake()
    end
end

Then when the entity spawn I set his ID to VentLastID + 1 and set VentLastID to VentLastId + 1.
Finally i used the ENT:Touch hook to print the entity's ID. But the only output I get is 1 even if I spawn a bunch of them.
as you can see on the screenshot bellow

https://files.facepunch.com/forum/upload/317004/4c31f8b7-e562-4fda-8830-bd3703c091a9/screenshot.png

So here is my shared.lua

ENT.Type = "anim"
ENT.Base = "base_gmodentity"

ENT.PrintName= "Vent"
ENT.Spawnable = true
ENT.AdminOnly = true
ENT.Author  = "The French Spy"

ENT.linked = 0

function ENT:SpawnFunction( ply, tr, ClassName )
    if ( !tr.Hit ) then return end
    local ent = ents.Create( ClassName )
    ent:SetPos( tr.HitPos + tr.HitNormal * 16 )
    ent:Spawn()
    ent.id = VentLastId + 1
    VentLastId = VentLastId + 1
    return ent
end

function ENT:Touch( entity )
    if self.linked == 0 then
        print( entity.id )
    end
end

If someone know what is wrong it would be very helpfull

[CupCakeR]

You reset VentLastId to 0 because ENT.Initialize get's called too.

Use this instead:
VentLastId = VentLastId or 0

[The French Spy]

Thanks for your solution but I had to use an other method wich finally worked but i'm facing another problem with the variable VentLastId.

So, when I put two entities each of them have their ID set, for the first one ID 1 and for the second ID 2, but when I start spawning more of them, like 3 or 4 they also get ID 1 and 2.
Here is my new shared.lua
ENT.Type = "anim"
ENT.Base = "base_gmodentity"

ENT.PrintName= "Vent"
ENT.Spawnable = true
ENT.AdminOnly = true
ENT.Author  = "The French Spy"

function ENT:Use( activator, caller )
    if self.set == nil then
        VentLastId = VentLastId + 1
        self.id = VentLastId
        self.set = 1
        caller:ChatPrint( "Vent set to ID " ..self.id )
    end
    if IsValid( activator ) and activator:IsPlayer() then
        if self.linked != nil then
            caller:ChatPrint( "Linked to vent " ..self.LinkedVent )
        end
    end
end

function ENT:Touch( entity )
    if self.linked == nil then
        if entity.linked == nil then
            if entity.id != nil then
                self.LinkedVent = entity.id
                if entity.LinkedVent != nil then
                    entity.LinkedVent = self.id
                    self.linked = 1
                    if entity.linked != 1 then
                        entity.linked = 1
                    end
                end
            end
        end
    end
end

And here is my init.lua
AddCSLuaFile( "cl_init.lua" )
AddCSLuaFile( "shared.lua" )
include('shared.lua')

function ENT:Initialize()
    self:SetModel( "models/props_junk/vent001.mdl" )
    self:PhysicsInit( SOLID_VPHYSICS )
    self:SetMoveType( MOVETYPE_VPHYSICS   )
    self:SetSolid( SOLID_VPHYSICS )
    self:SetUseType(SIMPLE_USE)
    if VentLastID == nil then
        VentLastId = 0
    end
    local phys = self:GetPhysicsObject()
    if (phys:IsValid()) then
        phys:Wake()
    end
end

[ButterKing5000]

Use Entity/NetworkVar to handle setting/getting the ID. Far easier and ensures the data is synced between the client and server. Only set the ID on the server and it will be updated on all clients.