Incomplete solution for http://facepunch.com/showthread.php?t=1463733

Entity PhysicsCollide Callback.lua

-- Run this on server, not client-side!
if not SERVER then
    error('Run this on the server-side (lua_openscript)!')
end
-- Find all "func_breakable" entities, and store the result into local "func_breakables" variable.
local func_breakables = ents.FindByClass('func_breakable')
if #func_breakables < 1 then
    -- Throws an error if none were founded.
    error('No "func_breakable" entities were founded.')
end
-- Adds a function callback for each "func_breakable" entity in the game.
for k, v in pairs(func_breakables) do
    v:AddCallback('PhysicsCollide', function(ent, data)
                                        print(ent)
                                        PrintTable(data)
                                        if not IsValid(ent) or not IsValid(data.HitEntity) or not ent:IsPlayer() then
                                            return
                                        end
                                        -- Do not use "v" here, instead use "data.HitEntity" which is the entity that ent is colliding with.
                                        -- Assuming you have called your Player metamethod "CanPassThroughFuncBreakables", which returns either true or false.
                                        -- ent is a collidee (it should be the player).
                                        data.HitEntity:SetNotSolid(ent:CanPassThroughFuncBreakables())
                                    end)
end