$a=array(
         0=>array(3=>9),
    1=>array(2=>9),
    2=>array(6=>5),
    3=>array(1=>15),
    4=>array(2=>4),
);

$b=array(
    0=>array(1=>15),
    1=>array(3=>9),
    2=>array(2=>9),
    3=>array(6=>5),
    4=>array(2=>4),
    );

$a=array(
    0=>array(3=>9),
    1=>array(2=>9),
    2=>array(6=>5),
    3=>array(1=>15),
    4=>array(2=>4),
);

foreach($a as $v) {
  $r[] = current($v);
  $k[] = key($v);
}

array_multisort($r, SORT_DESC, $k, SORT_DESC, $a);

print_r($a);

------解决方案--------------------
探讨

PHP code

$a=array(
    0=>array(3=>9),
    1=>array(2=>9),
    2=>array(6=>5),
    3=>array(1=>15),
    4=>array(2=>4),
);

foreach($a as $v) {
  $r[] = current($v);
  $k[] = key($v);
}
……


------解决方案--------------------
  受教了

------解决方案--------------------
我的博客里正好有一个，相比起来1楼的就是小儿科

------解决方案--------------------
不换药
PHP code

……
usort($a, create_function('$m, $n', 'return current($m)==current($n) ? (key($m)==key($n) ? 0 : key($m)<key($n)) : current($m)<current($n);'));
print_r($a);
/**
(
    [0] => Array
        (
            [1] => 15
        )

    [1] => Array
        (
            [3] => 9
        )

    [2] => Array
        (
            [2] => 9
        )

    [3] => Array
        (
            [6] => 5
        )

    [4] => Array
        (
            [2] => 4
        )

)
/**/