How do I reduce this function into a recursive one? - php

Question

I have a function that returns an array with empty keys from the input array. The problem is that I've been working on an inconsistent data. The data could go to any level of nested array. For example,
$inputArray = [
'a' => 'value a',
'b' => [
1 => [],
2 => 'value b2',
3 => [
'x' => 'value x'
'y' => ''
],
'c' => ''
],
];
I need an output that converts this kind of data to string. So,
$outputArray = [
'empty' => [
'b[1]',
'b[3][y]',
'c'
]
];
Here's what I have so far to get keys with empty values:
$outputArray = [];
foreach ($inputArray as $key => $value) {
if (is_array($value)) {
foreach ($value as $index => $field) {
if (is_array($field)) {
foreach ($field as $index1 => $value1) {
if (empty($value1)) {
array_push($outputArray['empty'], $key . '[' . $index . ']' . '[' . $index1 . ']');
}
}
}
if (empty($field)) {
array_push($outputArray['empty'], $key . '[' . $index . ']');
}
}
}
if (empty($value)) {
array_push($outputArray['empty'], $key);
}
}
return $outputArray;
As I said the input array could be nested to any level. I cannot keep on adding if (is_array) block every time the array is nested one more level. I believe it could be solved using a recursive function, but I cannot seem to figure out how. Please help me with this. Thanks.

Answer 1

You are right about a recursive function but you should also be aware of recursions, whether we are in or out of a recursion. The tricky part is passing current level keys to the recursive function:
function findEmpties($input, $currentLevel = null) {
static $empties = [];
foreach ($input as $key => $value) {
$levelItem = $currentLevel ? "{$currentLevel}[{$key}]" : $key;
if (empty($value)) {
$empties['empty'][] = $levelItem;
} else {
if (is_array($value)) {
findEmpties($value, $levelItem);
}
}
}
return $empties;
}
Live demo