PHP - Recursive Multidimension Array iterator

Question

I'm trying to write a recursive array iterator function in which the function will return a result set of all sets that are specified by '$needle'. Where $needle = key

Here is my function:

function recursive($needle, $array, $holder = array()) {
    foreach ($array as $key => $value) {
        if (gettype($value) == 'array') {
            if ($key != $needle) {
                recursive($needle, $value);
            } elseif ($key == $needle) {
                if (!empty($value)) {
                    array_push($holder, $value);
                }
            }
        }
    }
    return $holder;
}

But I'm not getting all the results back and instead get a few empty results, if I don't specify the !empty($value), although the input array does not have any empty sets. What am I doing wrong?

Answer 1

More fine-grained control is perhaps possible with true (tm) recursive array traversal via RecursiveIterator interface and some key filters and array conversion functions:

$needle = '0';
$array  = [[1]];

$it = new KeyFilter(
    new RecursiveIteratorIterator(
        new MyRecursiveArrayIterator($array)
        , RecursiveIteratorIterator::SELF_FIRST
    )
    , $needle
);

$result = iterator_to_array($it, FALSE);
var_dump($result);

Providing an exemplary result as:

array(2) {
  [0] =>
  array(1) {
    [0] =>
    int(1)
  }
  [1] =>
  int(1)
}

Full code example (Demo):

<?php
/**
 * @link http://stackoverflow.com/q/19709410/367456
 */

Class MyRecursiveArrayIterator extends ArrayIterator implements RecursiveIterator
{
    public function hasChildren()
    {
        $current = $this->current();
        return is_array($current) && count($current);
    }

    public function getChildren()
    {
        return new self($this->current());
    }
}

class KeyFilter extends RegexIterator
{
    public function __construct(Iterator $iterator, $key)
    {
        parent::__construct(
            $iterator, '/' . preg_quote($key) . '/', NULL, RegexIterator::USE_KEY
        );
    }
}

$needle = '0';
$array  = [[1]];

$it = new KeyFilter(
    new RecursiveIteratorIterator(
        new MyRecursiveArrayIterator($array)
        , RecursiveIteratorIterator::SELF_FIRST
    )
    , $needle
);

$result = iterator_to_array($it, FALSE);
var_dump($result);

Answer 2

You don't need to reinvent the wheel since PHP has standard Recursive Iterator API:

//$array is your multi-dimensional array
$result   = [];
$search   = 'foo';
$iterator = new RecursiveIteratorIterator(
    new RecursiveArrayIterator(
        $array,
        RecursiveArrayIterator::CHILD_ARRAYS_ONLY
    )
); 

foreach($iterator as $key=>$value)
{
   if($search==$key && $value!=='')
   {
      $result[] = $value;
   }
}

-note, that, since you're searching for value by key - in common case $value will hold entire subsection.

If you want to do this in your own recursive function, here's one:

function recursive($needle, $array, $holder = []) 
{
    $holder = [];
    foreach($array as $key=>$value)
    {
       if($key===$needle && $value!=='')
       {
          $holder = array_merge($holder, [$value]);
       }
       if(is_array($value))
       {
          $holder = array_merge($holder, recursive($needle, $value, $holder));
       }
    }
    return $holder;
}

Answer 3

A tiny modification of your construction:

$holder = recursive($needle, $value, $holder);

Ay?