arrays - PHP 連想配列のソート

Question

連想配列の要素をソートしたいと思います。現在、私の配列は次のようになっています。

Array
(
    [1585] =>  Chicago, Ohio,Dallas, Denver, Detroit, Houston, Las Vegas, So. Calf.
    [1586] =>  Chicago, Ohio, Dallas, Denver, Houston, Las Vegas, So. Calf.
    [1588] =>  The Bay Area, Chicago, Dallas, Detroit, Houston, Las Vegas, Minneapolis
    [1589] =>  Charlotte, Chicago, Ohio, D.C.
    [1590] =>  Orange County, Orlando, Philadelphia, Phoenix, Richmond, San Diego, The Bay Area, Seattle
   )

この配列を次のように昇順にしたいのですが：

Array
(
    [1585] =>  Chicago, Dallas, Denver, Detroit,Houston, Las Vegas, Ohio, So. Calf.
    [1586] =>  Chicago, Dallas, Denver, Houston, Las Vegas,, Ohio, So. Calf.
    [1588] =>  Chicago, Dallas, Detroit, Houston, Las Vegas, Minneapolis, The Bay Area
    [1589] =>  Charlotte, Chicago, D.C., Ohio
    [1590] =>  Orange County, Orlando,Philadelphia, Phoenix, Richmond,San Diego, Seattle, The Bay Area
   )

ありがとう ....