我有以下数组：
Array
(
[0] => Array
(
[Outcome] => 1
[Bookmaker] => PaddyPower
[Updated] => 2015-01-19T09:28:36
[Bet] => 1
[SP] => 4/5
[CP] => 17/20
[line] =>
[Decimal] => 0.85
)
[1] => Array
(
[Outcome] => 1
[Bookmaker] => BetFair
[Updated] => 2015-01-19T09:59:12
[Bet] => 1
[SP] => 1/25
[CP] => 43/50
[line] =>
[Decimal] => 0.86
)
[2] => Array
(
[Outcome] => 1
[Bookmaker] => BetVictor
[Updated] => 2015-01-19T10:29:38
[Bet] => 1
[SP] => 869/1000
[CP] => 869/1000
[line] =>
[Decimal] => 0.87
)
[3] => Array
(
[Outcome] => 1
[Bookmaker] => BetFred
[Updated] => 2015-01-19T09:28:30
[Bet] => 1
[SP] => 4/5
[CP] => 17/20
[line] =>
[Decimal] => 0.85
)
[4] => Array
(
[Outcome] => 1
[Bookmaker] => CoralBet
[Updated] => 2015-01-19T09:28:36
[Bet] => 1
[SP] => 73/100
[CP] => 83/100
[line] =>
[Decimal] => 0.83
)
[5] => Array
(
[Outcome] => 1
[Bookmaker] => Bet365
[Updated] => 2015-01-19T09:35:59
[Bet] => 1
[SP] => 73/100
[CP] => 83/100
[line] =>
[Decimal] => 0.83
)
[6] => Array
(
[Outcome] => 1
[Bookmaker] => WilliamHill
[Updated] => 2015-01-19T09:48:17
[Bet] => 1
[SP] => 4/5
[CP] => 83/100
[line] =>
[Decimal] => 0.83
)
[7] => Array
(
[Outcome] => 1
[Bookmaker] => SkyBet
[Updated] => 2015-01-19T09:29:48
[Bet] => 1
[SP] => 67/100
[CP] => 83/100
[line] =>
[Decimal] => 0.83
)
[8] => Array
(
[Outcome] => 1
[Bookmaker] => Ladbrokes
[Updated] => 2015-01-19T09:29:48
[Bet] => 1
[SP] => 3/4
[CP] => 4/5
[line] =>
[Decimal] => 0.8
)
)
我正在尝试按"十进制"键的值对其进行排序。
我创建了一个函数来按十进制值进行排序，但由于某种原因，正如您在上面的数组中看到的那样，它并没有完全排序，因为 0.86 比 0.85 更好的值。
usort($outcomes, 'sort_by_decimal');
function sort_by_decimal ($a, $b)
{
return $a['Decimal'] - $b['Decimal'];
}
谢谢。
你快到了。再次阅读usort()文档页面。它在关于参数value_compare_func描述的说明中说：
int callback ( mixed $a, mixed $b )谨慎
从比较函数返回非整数值（如浮点数）将导致回调返回值的内部强制转换为整数。因此，诸如 0.99 和 0.1 之类的值都将转换为整数值 0，这将比较此类值为相等。
现在我认为很明显，你的函数应该读成这样：
function sort_by_decimal ($a, $b)
{
if ($a['Decimal'] < $b['Decimal']) {
return -1;
} elseif ($a['Decimal'] > $b['Decimal']) {
return +1;
} else {
return 0;
}
}