How to get the value of a column in a multidimensional array?

[
    "id" => 7
    "parent_id" => 9
    "child_id" => 11
    "children" => [
      0 =>  [
        "id" => 4,
        "parent_id" => 11,
        "child_id" => 2
      ]
      1 =>  [
        "id" => 5,
        "parent_id" => 11,
        "child_id" => 3
      ]
      2 =>  [
        "id" => 6,
        "parent_id" => 11,
        "child_id" => 4
      ]
    ]
  ]
  1 =>  [
    "id" => 8,
    "parent_id" => 10,
    "child_id" => 11
    "children" => [
      0 =>  [
        "id" => 4,
        "parent_id" => 11,
        "child_id" => 2
      ]
      1 =>  [
        "id" => 5,
        "parent_id" => 11,
        "child_id" => 3
      ]
      2 =>  [
        "id" => 6,
        "parent_id" => 11,
        "child_id" => 4
      ]
    ]
  ]

the generation rules are as follows
the child_id under parent_id- > child_id- > children of each object is an array
above the result is 

[[9,11,2,3,4],[10,11,2,3,4]]
Php
Apr.05,2021 
$arr = [
  [
    "id" => 7,
    "parent_id" => 9,
    "child_id" => 11,
    "children" => [
      [
        "id" => 4,
        "parent_id" => 11,
        "child_id" => 2
      ],
      [
        "id" => 5,
        "parent_id" => 11,
        "child_id" => 3]
      ,
      [
        "id" => 6,
        "parent_id" => 11,
        "child_id" => 4
      ]
    ]
  ],
  [
    "id" => 8,
    "parent_id" => 10,
    "child_id" => 11,
    "children" => [
      [
        "id" => 4,
        "parent_id" => 11,
        "child_id" => 2
      ], [
        "id" => 5,
        "parent_id" => 11,
        "child_id" => 3
      ], [
        "id" => 6,
        "parent_id" => 11,
        "child_id" => 4
      ]
    ]
  ]
];

$result = array_map(function ($item) {
  return array_merge([$item['parent_id'], $item['child_id']], array_map(function ($item) {
    return $item['child_id'];
  }, $item['children']));
}, $arr);

print_r($result);

Previous: How does the hmset in redis set the timeout for a key?

Next: Callback in scrapy is useless. I have read the relevant problems on seg, but I can't solve them. I hope you can answer them.

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1bf98b4-31907.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1bf98b4-31907.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?