-- Create table
local items = {}

--Let's put stone ID at index "stone"
items['stone'] = 1

--And torch at 50
items['torch']= 50

-- Searching function
local function search(table, toSearch)
    -- Check if given table is actually table
    if type(table) ~= "table" then
        -- If it's not, raise error
        error("Table expected, got "..type(table) or "nil", 2)
    end

    -- Loop trough all values in given table
    -- Set "index" to current item's index and set "value" to current item's value
    for index, value in pairs(table) do
        -- If we fount it
        if index == toSearch then
            -- Return fount value
            return value
        end
    end

    -- If we reached this point it meas that items was not fount
    -- Return false since nothing was fount
    return false
end

-- Some testing

-- Search for "stone" in table "items"
print(tostring(search(items, "stone"))) --> 1

print(tostring(search(items, "noSuchThing"))) --> false

-- Search inside nil
search(nil, "stone")