not getting the desired output from an array

I need to create an dynamic array and can't get it right. I need something like this:

Product Name

• top
• • White
• • Black
• Bottom
• • Red
• • Green

I came up with this code, which is producing the above text, so my logic must be about right.

$set = array();
$set['name'] = "Product Name";

$options = array("top", "bottom");
$values['top'] = array("White", "Black");
$values['bottom'] = array("Red", "Green");

echo "<pre>".$set['name']."</pre>";
foreach ($options as $o) {
    echo "<pre>- $o</pre>";
    $set['options'][]['name'] = $o;

    foreach ($values[$o] as $v) {
        echo "<pre>-- $v</pre>";
        $set['options'][]['values']['name'] = $v;
    }
}

The array that is created with the above code is:

Array
(
  [name] => Product Name
  [options] => Array
  (
    [0] => Array
    (
     [name] => top
    )
[1] => Array
                (
                    [values] => Array
                        (
                            [name] => White
                        )

                )

            [2] => Array
                (
                    [values] => Array
                        (
                            [name] => Black
                        )

                )

            [3] => Array
                (
                    [name] => bottom
                )

            [4] => Array
                (
                    [values] => Array
                        (
                            [name] => Red
                        )

                )

            [5] => Array
                (
                    [values] => Array
                        (
                            [name] => Green
                        )
                )
        )
)

THe output I want is:

Array
(
    [name] => Product Name
    [options] => Array
        (
            [0] => Array
                (
                    [name] => top
                    [values] => Array
                        (
                            [0] => Array
                                (
                                    [name] => White
                                )

                            [1] => Array
                                (
                                    [name] => Black
                                )

                        )

                )

            [1] => Array
                (
                    [name] => bottom
                    [values] => Array
                        (
                            [0] => Array
                                (
                                    [name] => Red
                                )

                            [1] => Array
                                (
                                    [name] => Green
                                )

                        )

                )

        )

)

What am I missing ?