add key value pair to dynamic multidimensional array in php - php

Question

I have a multidimensional array as per below example which I want to search through for a specific value $needle. If this value is found I want to add a new key=> value pair for each node of the array branch where the $needle is subsequently found.
The needle should be unique but the depth of the sub arrays is dynamic.
Example:
$data= [
0=> [
'title' => 'alpha',
'children' => [],
],
1 =>[
'title' => 'beta',
'children' => [
0=>[
'title' => 'charlie',
'children' => [],
],
1=>[
'title' => 'delta',
'children' => [],
],
2=>[
'title' => 'echo',
'children' => [
0=>[
'title' => 'foxtrot',
'children' => [],
],
],
],
],
],
2 => [
'title' => 'gulf',
'children' => []
]
Now when I search for $needle= foxtrot I want to add to each of the subarrays "active" => 1
e.:
$data= [
0=> ...
1 =>[
'title' => 'beta',
**'active' => 1,**
'children' => [
0=>[
'title' => 'charlie',
'children' => [],
],
1=>[
'title' => 'delta',
'children' => [],
],
2=>[
'title' => 'echo',
**'active' => 1,**
'children' => [
0=>[
'title' => 'foxtrot',
**'active' => 1,**
'children' => [],
],
],
],
],
],
My not working attempt. I don't know how I correctly merge the key => value on each finding:
function array_mod_active($array, $needle, $parent_key='' )
{
foreach($array as $key => $value) {
if (is_array($value)) {
array_mod_active($value, $needle, $key );
} elseif ($value === $needle) {
array_merge(array('active' => 1), $array[$parent_key]);
}
}
return $array;
}

Answer 1

This is one recursive way to do it. I've added inline comments to explain each step.
Code: (Demo)
function keysort($a,$b){ // this function is optional; purely used for aesthetic/readability purposes
$order=['title'=>0,'active'=>1,'children'=>2]; // order keys by this specific order
return $order[$a]<=>$order[$b];
}
function activate_lineage(&$array,$needle){
foreach($array as &$item){
if($item['title']==$needle){ // $needle located, make active
$item['active']=1; // add active element
uksort($item,'keysort'); // optional call
return $array; // send full updated array back where it came from
}elseif(!empty($item['children'])){ // drill down if there are any children
$copy=$item; // preserve original (this avoids a post-recursion column-search)
$item['children']=activate_lineage($item['children'],$needle); // recurse
if($copy!==$item){ // if children subarray was updated, a child was activated
$item['active']=1; // add active element
uksort($item,'keysort'); // optional call
break; // don't continue the loop; only one parent will be activated (per level)
}
}
}
return $array; // return the full array, no matter what level it is on
}
// to call:
var_export(activate_lineage($data,'foxtrot'));
/* or because the function modifies by reference...
activate_lineage($data,'foxtrot');
var_export($data);
*/