教えてください。

$a = array("あ",0,"い","う","え","お");
$b = array("か",7,"き","く","け","こ");
$c = array("さ",9,"し","す","せ","そ");
$d = array("た",1,"ち","つ","て","と");
$e = array("な",5,"に","ぬ","ね","の");
$f = array("は",6,"ひ","ふ","へ","ほ");

という$a〜$fの配列を、数字順に$a,$d,$e,$f,$b,$cという風に
並び替えたいのですが、スマートに書けません。
どんな書き方が負荷のかからないスマートな書き方なんでしょうか？