local PhaseEnabled = true -- will it be enabled or not (true or false)
local Players = game:GetService("Players")
local RunService = game:GetService("RunService")
local LocalPlayer = Players.LocalPlayer
local CachedParts = {}
local RunLoops = {StepTable = {}}

function RunLoops:BindToStepped(name, func)
    if RunLoops.StepTable[name] == nil then
        RunLoops.StepTable[name] = RunService.Stepped:Connect(func)
    end
end

function RunLoops:UnbindFromStepped(name)
    if RunLoops.StepTable[name] then
        RunLoops.StepTable[name]:Disconnect()
        RunLoops.StepTable[name] = nil
    end
end

local function IsAlive(Player, headCheck)
    Player = Player or LocalPlayer
    if Player and Player.Character and Player.Character:FindFirstChildOfClass("Humanoid") and Player.Character:FindFirstChild("HumanoidRootPart") and (not headCheck or Player.Character:FindFirstChild("Head")) then
        return true
    else
        return false
    end
end

if getgenv then
    getgenv().Phase = {Enabled = PhaseEnabled}
else
    _G.Phase = {Enabled = PhaseEnabled}
end

while IsAlive() do
    if Phase.Enabled then -- no need for 'getgenv().Phase.Enabled' or '_G.Phase.Enabled' since you just can do 'Phase.Enabled', it will make your code look better, more readable and just cool
        if not RunLoops.StepTable.Phase or RunLoops.StepTable.Phase == nil then
            RunLoops:BindToStepped("Phase", function()
                for _, v in pairs(LocalPlayer.Character:GetChildren()) do 
                    if v:IsA("BasePart") and v.CanCollide then 
                        CachedParts[v] = true
                        v.CanCollide = false
                    end
                end
            end)
        end
    else
        for part in pairs(CachedParts) do
            if part:IsA("BasePart") then
                part.CanCollide = true
            end
        end
        CachedParts = {}
        RunLoops:UnbindFromStepped("Phase")
    end
    wait(0.1) -- delay to prevent high cpu usage and fps drop
end