添加到数组中的数组（构建数据组）

Question

在 PHP 中，我循环访问数据库中的结果，并且我想将结果分组，所以我有以下代码...

$query = $db->prepare('select groupid, myval1, myval2 from mytable');
$query->execute();
$query->bind_result($groupid, $myval1, $myval2);
$groups = [];
$currentgroup = null;
while ($query->fetch()) {
  if ($currentgroup == null || $currentgroup["groupid"] != $groupid) {
    $currentgroup = ["groupid" => $groupid, "values" => []];
    $groups[] = $currentgroup;
  }
  $currentgroup["values"][] = ["myval1" => $myval1, "myval2" => $myval2];
}
$query->close();

这导致$groups 数组包含每个特定组的单个项目，但values 数组仍然为空...

$groups = [
  ["groupid" = 1, "values" = []],
  ["groupid" = 2, "values" = []],
  ["groupid" = 3, "values" = []]
]

当我通过循环进行调试时，我可以看到 $currentgroup["values"] 正在正确填充，但似乎即使 $currentgroup 已添加到 $groups，这些值也不是填充。这向我表明正在使用不同的数组，但我看不到如何修复它......我想引用是必需的，但我正在努力弄清楚如何。

如何修复上述代码以导致...

$groups = [
  ["groupid" = 1, "values" = [
    ["myval1" = 1, "myval2" = 2],
    ["myval1" = 3, "myval2" = 4]
  ],
  ["groupid" = 2, "values" = [
    ["myval1" = 5, "myval2" = 6],
    ["myval1" = 7, "myval2" = 8],
    ["myval1" = 9, "myval2" = 10]
  ],
  ["groupid" = 3, "values" = []]
]

Answer 1

如果您通过groupid 为您的$groups 数组编制索引，那么您可以使用它来将值添加到正确的分组中。所以在你的循环内部变成......

if ( !isset($groups[$groupid]) ) {
    $groups[$groupid] = ["groupid" => $groupid, "values" => []];
}
$groups[$groupid]["values"][] = ["myval1" => $myval1, "myval2" => $myval2];

您可能想在最后删除这些组号，只需使用array_values() 即可...

$groups = array_values($groups);