次のような単純な配列をソートするのに苦労しています。
Array
(
    [3] => Array
        (
            [0] => EU West (Ireland)
            [1] => eu-west-1
        )
    [7] => Array
        (
            [0] => South America (Sao paulo)
            [1] => sa-east-1
        )
    [0] => Array
        (
            [0] => US East (Virginia)
            [1] => us-east-1
        )
    [4] => Array
        (
            [0] => Asia Pasific (Tokyo)
            [1] => ap-northeast-1
        )
    [2] => Array
        (
            [0] => US West (Oregon)
            [1] => us-west-2
        )
    [1] => Array
        (
            [0] => US West (N. California)
            [1] => us-west-1
        )
    [5] => Array
        (
            [0] => Asia Pasific (Singapore)
            [1] => ap-southeast-1
        )
    [6] => Array
        (
            [0] => Asia Pasific (Sydney)
            [1] => ap-southeast-2
        )
)
この配列をIndexでソートしたい。使用ksort()しましたが、動作しません。出力 1 のままです。