Array
(
    [test] => Array
        (
            [0] => Array
                (
                    [a] => Array
                        (
                            [0] => 1
                        )

                    [b] => Array
                        (
                            [0] => 2
                        )

                    [c] => Array
                        (
                            [0] => 3
                        )

Array
(
    [test] => Array
        (
            [0] => Array
                (
                    [a] => 1

                    [b] => 2

                    [c] => 3

function optimize( $config )
{
  foreach ( $config as $key => $value )
    if( is_array( $value ) && count( $value ) == 1 && isset( $value[0] ))
       $config[$key] = $value[0];

  return $config
}