How can I save table parameter?

I am writing a tiny RPG game, and I followed a tutorial to save my table.

But perhaps my English and coding ability are not good enough to understand the tutorial well.

I can’t save nor load data.

Please somebody corrects my code. Thank you very much.

here is website of the tutorial : 

http://omnigeek.robmiracle.com/2012/02/23/need-to-save-your-game-data-in-corona-sdk-check-out-this-little-bit-of-code/

and the following is my code. I want to save and load HP and coin.

local user = {HP = 300, coin = 0}

function save(filename, userValue)

    local path = system.pathForFile( filename, system.DocumentsDirectory)

    local file = io.open(path, “w”)

    if file then

        local contents = json.encode(userValue)

        file:write( contents )

        io.close( file )

    end

end

  

function load(filename)

    local path = system.pathForFile( filename, system.DocumentsDirectory)

    local contents = “”

    local userValue = {}

    local file = io.open( path, “r” )

    if file then

         local contents = file:read( “*a” )

        userValue = json.decode(contents);

         io.close( file )

     else

       userValue.HP = 300

       userValue.coin = 0

       save(userValue, “userValue.json”)

    end

end

    user = load(“user.json”)

  print(user.HP)

  print(user.coin)