Add item to parent item within a multi dimensional array - php

Question

I have a multi dimensional array, something like this:
$items = array(
'one' => array(
'a' => array(),
'b' => array(),
'c' => array()
),
'two' => array(
'd' => array(),
'e' => array(),
'f' => array()
),
'three' => array(
'g' => array(),
'h' => array(),
'i' => array()
)
);
So, I could add another array within the tree structure as:
$items['one']['c'][] = array( 'j' => array() );
But if I don't know that c is within one, how can I achieve this? I've looked at array_search but that just returns false. I think that is because what I'm looking for isn't at the top level of the array perhaps?
I know that c exists, but I don't know which sub-array it's in and how far down it goes. Is this possible?

Answer 1

If I understand you correctly, this function will do what you want:
<?php
$items = array(
'one' => array(
'a' => array(),
'b' => array(),
'c' => array()
),
'two' => array(
'd' => array(),
'e' => array(),
'f' => array()
),
'three' => array(
'g' => array(),
'h' => array(),
'i' => array()
)
);
function addToSub($items, $key, $addItem) {
foreach($items as &$item) {
if (in_array($key, array_keys($item))) {
$item[$key][] = $addItem;
}
}
return $items;
}
$items = addToSub($items, 'c', array( 'j' => array() ));
echo "<pre>";
var_dump($items);
echo "</pre>";
output:
array(3) {
["one"]=>
array(3) {
["a"]=>
array(0) {
}
["b"]=>
array(0) {
}
["c"]=>
array(1) {
[0]=>
array(1) {
["j"]=>
array(0) {
}
}
}
}

Answer 2

I think you are implementing a tree.
Your first thing to do is to find the node to append a child.
(In your example, the node is c and the child is j)
Implementing DFS search by recursion, I wrote following code.
(Make sure the node you're searching exists, or the function will return empty array)
<?php
$arr = [
'one' => [
'a' => [],
'b' => [],
'c' => [],
],
'two' => [
'd' => [],
'e' => [],
'f' => [],
],
'three' => [
'g' => [],
'h' => [],
'i' => [],
],
];
$arr = insertArr($arr, 'c', 'j');
print_r($arr);
function insertArr(array $arr, string $key, string $new): array {
// If key is found in $arr, append the child and return it.
if (array_key_exists($key, $arr)) {
$arr[$key][$new] = [];
return $arr;
}
// search the key in child node(next dimention)
foreach ($arr as $subArrKey => $subArr) {
// result will be empty if the key is not in child $subArr
$result = insertArr($subArr, $key, $new);
if (!empty($result)) {
// If the key is found in $subArr,
// replace $subArr with $result,
// which is the same as the $subArr but appended with child.
$arr[$subArrKey] = $result;
return $arr;
}
}
return [];
}
Now, you can append 'k' to either 'one', 'c' or 'j'.
To append 'k' to 'j', simply write:
$arr = insertArr($arr, 'j', 'k');

Answer 3

array_search will look for a value and in your example all your sub arrays are empty.
If I am not mistaken you could use array_map and for each subarray check if the key exists that you are looking for with array_key_exists:
$result = array_map(function($item) {
if (array_key_exists("c", $item)) {
$item["c"]["j"] = [];
}
return $item;
}, $items);
Demo