嵌套的数组.第三层正在消失

Question

我有这个数组:

$a = array(
    "7" => array(
        "id" => 7,
        "parent" => 6
    ),
    "6" => array(
        "id" => 6,
        "parent" => 5
    ),
    "5" => array(
        "id" => 5,
        "parent" => 4
    ),
    "4" => array(
        "id" => 4,
        "parent" => 0
    ),
    "3" => array(
        "id" => 7,
        "parent" => 2
    ),
    "2" => array(
        "id" => 7,
        "parent" => 1
    ),
    "1" => array(
        "id" => 7,
        "parent" => 0
    )
);

我想要的结果是:

$a = array(
    "4" => array(
        "id" => 4,
        "parent" => 0,
        array(
            "5" => array(
                "id" => 5,
                "parent" => 4,
                array(
                    "6" => array(
                        "id" => 6,
                        "parent" => 5,
                        array(
                            "7" => array(
                                "id" => 7,
                                "parent" => 6
                            )
                        )
                    )
                )
            )
        )
    ),
    "2" => array(
        "id" => 7,
        "parent" => 1,
        array(
            "3" => array(
                "id" => 7,
                "parent" => 2
            )
        )
    ),
    "1" => array(
        "id" => 7,
        "parent" => 0
    )
);

我使用的代码是这样的:

foreach($a as $v)
{
    if(isset($a[$v['PARENT']]))
    {
        $a[$v['PARENT']][$v['ID']] = $v;
        unset($a[$v['ID']]);
    }
}

问题是我得到了这个结果:

$a = array(
    "4" => array(
        "id" => 4,
        "parent" => 0,
        array(
            "5" => array(
                "id" => 5,
                "parent" => 4
            )
        )
    ),
    "2" => array(
        "id" => 7,
        "parent" => 1,
        array(
            "3" => array(
                "id" => 7,
                "parent" => 2
            )
        )
    ),
    "1" => array(
        "id" => 7,
        "parent" => 0
    )
);

Answer 1

要解决这个问题，你需要正确理解PHP中的变量引用/别名是如何工作的。

看下面的示例代码，它看起来和你的代码没有太大的不同，但是使用引用来访问任何父节点，即使它已经"移动"了:

# transform $flat into a tree:
foreach($flat as $id => &$value)
{
    # check if there is a parent
    if ($parentId = $value['parent'])
    {
        $flat[$parentId][0][$id] =& $value; # add child to parent
        unset($flat[$id]); # remove reference from topmost level
    }
}
unset($value); # remove iterator reference
print_r($flat); # your tree

$flat现在包含$flat中的所有值-但重新排序。演示。

Answer 2

您确定输出数组是正确的吗?当然，关键2应该是1的孩子(因为2有'parent'=>1)?如果不是这样，我就不明白我们到底在做什么，以及这些键是如何相互关联的。

如果2应该是1的子节点，这是有效的:

$keep = array();
foreach ($a as $k => &$v) {
  // Loop the array first time and create references to
  // structure the array how you want it
  if ($v['parent']) {
    $a[$v['parent']][0] = array($k => &$v);
  } else $keep[] = $k;
}
foreach ($a as $k => $v) {
  // Loop it again to get rid of non-root nodes from the root
  if (!in_array($k,$keep)) {
    unset($a[$k]);
  }
}
print_r($a);