PHP - 通过引用将子级添加到多级关联数组

Question

我有一个来自 MySQL 的记录集，它返回给定对象的类别 ID 及其值。例如：

+-----------+-------------+----------------+
| object_id | category_id | category_value |
+-----------+-------------+----------------+
|         1 |           2 | VEGETARIAN     |
|         1 |           3 | MATARÓ         |
|         1 |           5 | MARCO POLO     |
|         1 |           5 | JOHN DOE       |
|         2 |           2 | VEGETARIAN     |
|         2 |           3 | MATARÓ         |
|         2 |           5 | JOHN DOE       |
+-----------+-------------+----------------+

有了这个，我需要的是 PHP 中的以下结果关联数组：

// They are arrays, so more than one object_id can be in the same category tree (and the object_id can be repeated across categories)

$final_array['VEGETARIAN']['MATARÓ']['MARCO POLO'] = array(1);
$final_array['VEGETARIAN']['MATARÓ']['JOHN DOE'] = array(1, 2);

查询首先按object_id 对结果进行排序，然后再按category_id 和用户设置的顺序对结果进行排序。所以，它就像ORDER BY object_id ASC, FIELD(category_id, usercat1, usercat2, usercat3)（在这种情况下是FIELD(category_id, 2, 3, 5)。

我有每组都经过的循环，我试图保留一个临时变量来存储数组级别，因为它们可以更改（并不总是 3 级），所以类似于：

$temporary_array['VEGETARIAN'] = array();
$temporary_array = $temporary_array['VEGETARIAN'];

// And then, on the next iteration
$temporary_array['MATARÓ'] = array();
$temporary_array = $temporary_array['MATARÓ'];
// Now, $temporary_array would be equal to $temporary_array['VEGETARIAN']['MATARÓ'];

所以我可以根据 new 类别值创建一个主键，该值将存储为父数组的子级，并获取所有层次树。 每个级别都应包括所有下一个级别。

我尝试全局声明它并通过引用传递它，但它似乎不起作用。

有没有办法在 PHP 中实现这一点？你会怎样做才能得到想要的结果？

编辑：

我更接近于颠倒类别的顺序，所以我首先得到最后一个类别（其中没有其他类别的那个），然后我向上排列数组，如下所示：

// Long story very short, would be like
$final_array['new_category_value'] = $old_final_array; 

并为每个对象继续上升。当我更改object_id 时，我会：

array_merge_recursive($final_array, $actual_object_array);

但是，我仍然无法获得想要的结果。

感谢您的宝贵时间和 cmets！

Answer 1

假设您可以将 SQL 数据作为关联数组访问，并且“1”值是 object_id（而不是说 true/false 0/1 等），如下所示：

$sth = $dbh->prepare("SELECT ......"); //Your SQL Here
$sth->execute();
$rows = $sth->fetchAll(PDO::FETCH_ASSOC);

$rows 应该包含如下内容：

$rows = array(
    array(
        "object_id" => 1,
        "category_id" => 2,
        "category_value" => "VEGETARIAN"
    ),
    array(
        "object_id" => 1,
        "category_id" => 3,
        "category_value" => "MATARÓ"
    ),
    array(
        "object_id" => 1,
        "category_id" => 5,
        "category_value" => "MARCO POLO"
    ),
    array(
        "object_id" => 1,
        "category_id" => 5,
        "category_value" => "JOHN DOE"
    )
); 

从这一点开始，您可以遍历行。单个行发生的情况取决于它之前的行，因此存储并更新包含该行的变量，以便可以在此循环中访问它

//Define your final array
$final_array = array();

//Store a reference to the last row in order to get the last category checked
$lastRow=null;

//Store reference to the last potential parent 
$lastParent=&$final_array;

//Store a reference to the last entry - either an array or the object id
$lastEntry = null;


//Loop over all returned rows
foreach($rows as $row) {

    //If first time around loop, $lastRow will be null
    //If $lastRow is not null, but matches this row's category_id, we should add to the same parent 
    if($lastRow===null || $lastRow['category_id']===$row['category_id']){

        $lastParent[$row['category_value']] = $row['object_id'];

        $lastEntry = &$lastParent[$row['category_value']];

        //Note - Do not change last parent here
    }

    //lastCategoryId does not match this row's category ID and is not null, we must change the 
    //  last entry to be an array and add this entry to it.
    else {
        $lastParent = &$lastEntry;

        $lastParent = array($row['category_value'] => $row['object_id']);

        $lastEntry = &$lastParent[$row['category_value']];
    }


    //Loop complete, update the last row
    $lastRow=$row;
}

您现在可以检查调用 print_r($final_array);，它会返回：

Array
(
    [VEGETARIAN] => Array
        (
            [MATARÓ] => Array
                (
                    [MARCO POLO] => 1
                    [JOHN DOE] => 1
                )

        )

)