8

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?

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15
  • 3
    array_walk_recursive or array_search and lot more inbuilt function are there Commented Oct 31, 2013 at 14:40
  • 4
    We need an example array and function parameters that trigger your error. Otherwise, one cannot replicate the problem. Commented Oct 31, 2013 at 14:44
  • 2
    First thing that looks incomplete: You're assigning matches to $holder but $holder is not passed nor evaluated as a return value when calling recursive() from inside itself. Commented Oct 31, 2013 at 14:51
  • 2
    Apart from the notes, your flapsy comment "use any multidimensional array" made me actually do it and It proofs your function working - eval.in/private/236c41834864b6 - So at least sometimes :P - What's your concrete question? Commented Oct 31, 2013 at 14:53
  • 2
    Well, currently your recursive call does not do anything.. It's return value is ignored and it doesn't alter holder. So your whole function behaves as if only the elseif branch was there. Commented Oct 31, 2013 at 14:53

3 Answers 3

Reset to default
18

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;
}
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14 Comments

Actually this is not quite correct. There is the problem that RecursiveArrayIterator actually is a RecursiveArrayAndObjectIterator which is not what OP is looking or. Just saying.
@hakre hm. Not sure I got that. Where is the point against Iterator ?
No point against iterator, just perhaps (perhaps!) the wrong Iterator.
@dudemanbearpig: Oh good that at least you know when it is answered, because so far the question was not clear to most users. Which aparently is the reason as well that you're seeing life lessons here, just asking you for writing a question.
@hakre You can pass the RecursiveArrayIterator::CHILD_ARRAYS_ONLY flag to the RecursiveArrayIterator constructor as the second param to make it iterate only on arrays, making it actually RecursiveOnlyArrayIterator
|
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);
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Comments

0

A tiny modification of your construction:

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

Ay?

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3 Comments

That only passes the entire array into the function, ending up just spitting back the entire array as many times as it finds $needle...
Okay, so please be more specific with what you want to achieve with your function. Returning array elements that match your key? Or something else...?
And by the way: It doesn't pass the "entire array", it passes $holder which is initialized as empty array and then modified when (key == $needle) matches occur and those subsequent elements are pushed to it. As you said "a result set of all sets"...

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