PHP - Slice nested array - php

Question

I have two nested arrays with different length. I want to make length of second array as per first array, see below examples to get idea. Just remove all those items which don't exist in first array. Sometime second array has more values then first array, in this case my tree structure breaks.
These arrays are nested array so simple array_slice not working.
Here are the structure of array.
First Array
"1": {
"id": "1",
"username": "username",
"children": [
{
"id": "-1",
"username": "NULL",
"children": [
{
"id": "-1",
"username": "NULL",
"children": [
{
"id": "-1",
"username": "NULL",
"children": []
}
]
}
]
}
]
}
Second Array
"157": {
"id": "157",
"username": "test1",
"children": [
{
"id": "158",
"username": "test1",
"children": [
{
"id": "159",
"username": "test2",
"children": [
{
"id": "160",
"username": "test3",
"children": []
},
{
"id": "160",
"username": "KICK ME BECAUSE I M NOT EXIST IN FIRST ARRAY",
"children": []
}
]
}
]
},
{
"id": "160",
"username": "KICK ME BECAUSE I M NOT EXIST IN FIRST ARRAY",
"children": [
{
"id": "159",,
"username": "KICK ME BECAUSE I M NOT EXIST IN FIRST ARRAY",
"children": [
{
"id": "161",
"username": "KICK ME BECAUSE I M NOT EXIST IN FIRST ARRAY",
"children": []
}
]
}
]
}
]
}
Expected Output
"157": {
"id": "157",
"username": "test1",
"children": [
{
"id": "158",
"username": "test1",
"children": [
{
"id": "159",
"username": "test2",
"children": [
{
"id": "160",
"username": "test3",
"children": []
},
]
}
]
},
]
}
I am trying this method, but it is not working.
$firstCount = (array_map('count', $actualTree));
$secondCount = (array_map('count', $emptyTree));
$chunk = array_slice($actualTree, 0 , $second[$this->userId], true);
Use Case
The thing which I want to do is that remove those array childrens completely which are not exists in first array. I am building a binary tree upto three levels. First array already has a binary tree with empty values. The second array is data that is coming from the database, and I am simply replacing empty data with the actual data using array_replace. This is working good until second array has more values then first array. So to make it working I have to remove those extra elements.
Could anyone please help me to make there length same. Any help will be appreciated.
Thanks in advance.

Answer 1

A Stack Overflow miracle has occurred... I got a recursive snippet to work on the first pass! Usually it takes me a good hour or two to write something that works.
I don't know if I can make it any tighter/better OR if it will fail on any fringe cases, but:
it works for your sample input
it is midnight for me, I'm tired, and I have to work in the morning
Effectively, it synchronously & recursively iterates each array and stores each level of the entry array to the output array so long as the same level keys exists in the structure array.
Code: (Demo)
function truncateRecursive($structure, $entry) {
$output = [];
while (($structureKey = key($structure)) !== null && ($entryKey = key($entry)) !== null) {
$output[$entryKey] = !is_array($entry[$entryKey])
? $entry[$entryKey]
: truncateRecursive($structure[$structureKey], $entry[$entryKey]);
unset($structure[$structureKey], $entry[$entryKey]);
}
return $output;
}
var_export(truncateRecursive($structure, $entry));
Output:
array (
157 =>
array (
'id' => '157',
'username' => 'test1',
'children' =>
array (
0 =>
array (
'id' => '158',
'username' => 'test1',
'children' =>
array (
0 =>
array (
'id' => '159',
'username' => 'test2',
'children' =>
array (
0 =>
array (
'id' => '160',
'username' => 'test3',
'children' =>
array (
),
),
),
),
),
),
),
),
)