keys - php array_walk

Error de PHP ¿Por qué es "variable undefined" dentro de array_map?

Question

Estoy usando la función array_map en mi aplicación php. Definí la función array_map de esta manera.

$ratingID =  $this->db->insert_id();

    $rated_item_array = array_map(function ($a) {
        return $a + array(''RatingID'' => $ratingID);
    }, $rated_item_array);  

Aviso de php viene

A PHP Error was encountered

Severity: Notice

Message: Undefined variable: ratingID

Cuando $ratingID el $ratingID . Imprime el valor correctamente, por lo que se define $ ratingID. ¿Por qué no está definido en la función array_map ? Mi $rated_item_array es

Array
(
    [0] => Array
        (
            [RatingFactorPreferenceID] => 1,
            [PreferenceID] => 45,
            [RatedValue] => 1,
            [CreatedOn] => 1326790338,
            [CreatedBy] => 25
        )

    [1] => Array
        (
            [RatingFactorPreferenceID] => 2,
            [PreferenceID] => 45,
            [RatedValue] => 1,
            [CreatedOn] => 1326790338,
            [CreatedBy] => 25
        )

    [2] => Array
        (
            [RatingFactorPreferenceID] => 3,
            [PreferenceID] => 45,
            [RatedValue] => 1,
            [CreatedOn] => 1326790338,
            [CreatedBy] => 25
        )
)

Answer 1

$rated_item_array = array_map(
  function ($a) use ($ratingID){ 
    return $a + array(''RatingID'' => $ratingID ); 
  }, 
  $rated_item_array
);