Question

在我的PHP应用程序中查找错误时，我遇到了一些奇怪的行为。这是一个代码示例：

$x = array(array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'),
           array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'),
           array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'),
           array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'));
$test = array();

$i = 0;
foreach ($x as $key => $value) {
    $test[$i] = $value;
    $test[$i]['t6'] = $i++;
}
print_r($test);

预期输出如下：

Array
(
    [0] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
            [t6] => 0
        )

    [1] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
            [t6] => 1
        )

    [2] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
            [t6] => 2
        )

    [3] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
            [t6] => 3
        )

)

我得到的是：

Array
(
    [0] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
        )

    [1] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
        )

    [2] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
        )

    [3] => Array
        (
            [t1] => a
            [t2] => b
            [t3] => c
            [t4] => d
            [t5] => e
        )

    [4] => Array
        (
            [t6] => 3
        )

)

当我更改行

时

$test[$i]['t6'] = $i++;

到

$test[$i]['t6'] = $i;
$i++;

它按预期工作。

我正在尝试了解问题的原因，所以我可以在类似的情况下避免它。有人可以解释为什么这里没有正确分配增量吗？

（顺便说一下，减量存在同样的问题。也许这是一个有用的信息和平。）

Answer 1

您遇到语义错误，请尝试使用$ key而不是$ i

$x = array(array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'),
           array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'),
           array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'),
           array('t1' => 'a', 't2' => 'b', 't3' => 'c', 't4' => 'd', 't5' => 'e'));
$test = array();

$i = 0;
foreach ($x as $key => $value) {
    $test[$key] = $value;
    $test[$key]['t6'] = $i++;
}
print_r($test);

?>

Answer 2

我最终自己找到了答案。分配似乎不起作用的原因是++和（数组）的运算符优先级是相同的，并且关联性是正确的。（http://www.php.net/manual/en/language.operators.precedence.php）

这意味着$ i在用作数组键之前会递增。这意味着foreach循环的下一次迭代将覆盖行

中的相同键

$test[$key] = $value;

唯一没有发生的事情是在循环的最后一次迭代中。

作为修复，我可以写

$test[$i++]['t6'] = $i;

看起来很奇怪，反直觉，或者我可以使用我的原始修复

$test[$i]['t6'] = $i;
$i++;

虽然不那么优雅，但更容易阅读。

将增量分配给数组

2 个答案: