Recursively search a multidimensional array for the parent key of a matched key or value

Question

I am trying to search a multidimensional array, where when I search for a value it should return me its parent key. Array looks like this:

[
  "fruits" => [
     "sweet" => [
       "apple",
       "banana",
     ],
     "citrus" => [
       "lemon",
       "orange",
     ]
   ],
   "vegetables" => [
     "leafy" => [
       "spinach",
       "broccoli",
     ]
   ],
]

I want the function to return leafy when I search for broccoli or if I search for leafy then it should return vegetables but this function always return me null:

function recursiveFind(array $haystack, $needle)
{
    $foundKey = null;
    foreach ($haystack as $key => $value) {        

        if(is_array($value)) {
            if(in_array($needle, $value)){
                return $key;
            } else {
                $foundKey = recursiveFind($value, $needle);
            }
        }

    }
    return $foundKey;
}

One more function I tried is as below, which returns me false always:

function recursiveFind(array $haystack, $needle)
{
        foreach($haystack as $key => $value) {
            $current_key = $key;
            if($needle === $value || (is_array($value) && recursiveFind($value, $needle) !== false)) {
                return $current_key;
            }
        }
        return false;
}

Above function works when there is only second level for example if we remove fruits and vegetable wrappers.

Answer 1

function recursiveFind(array $haystack, $needle)
{
   foreach($haystack as $key => $data){
        foreach($data as $k=>$v){
            if($needle==$k){
                return $key;
            }
            if(in_array($needle, $v)){
                return $k;
            }
        }
    }
    return null;
}

As per your requirement specified in comments-

 public $needle = 'citrus';

private function recursiveFind($haystack, $prev)
{
    foreach ($haystack as $key => $data) {
        if (is_array($data) && in_array($this->needle, $data)) {
            return $key;
        }
        if ($this->needle === $key) {
            return $prev;
        }
        if (is_array($data)) {
            $result = $this->recursiveFind($data, $key);
            if ($result != null)
                return $result;
        }
    }

    return null;
}

And call this like-

$value = $this->recursiveFind($data, null);

return $value;

Notice that I have declared $needle as a class variable. You can set this field anything you want now.

Happy Coding :)

Answer 2

Please check this updated code,

<?php

$data = [
    "fruits" => [
        "sweet" => [
            "apple",
            "banana",
        ],
        "citrus" => [
            "lemon",
            "orange",
        ]
    ],
    "vegetables" => [
        "leafy" => [
            "spinach",
            "broccoli",
        ]
    ],
];

function recursiveFind(array $datas, $needle) {
    foreach ($datas as $key => $data) {
        foreach ($data as $inx => $stx) {
            if ($needle == $inx) {
                return $key;
            }
            if (in_array($needle, $stx)) {
                return $inx;
            }
        }
    }
    return null;
}

echo $parentkey = recursiveFind($data, 'broccoli'); // output: leafy
echo $parentkey = recursiveFind($data, 'leafy'); // output: vegetables
?>

Answer 3

function recursive_return_array_value_by_key($needle, $haystack){
   $return = false;
   foreach($haystack as $key => $val){
      if(is_array($val)){
         $return = recursive_return_array_value_by_key($needle, $val);
      }
      else if($needle === $key){
        return "$val\n";
      }
    }
    return $return;
  }