Create seperate sub array based on array key

Question

I need to separate a single array into sub arrays based on the amount of times > appears within the array key so that I tell who is a parent category and who isn't. Note that there is no limit to the amount of possible nested parents.

Also, if a child with the same name exists, it is considered unique if it has a different parent.

My source array structure looks like this:

array (
  'Test Parent 2&gt;Test Child&gt;Test Sub Child' => 
  array (
    'content_id_4' => NULL,
  ),
  'Test Parent 3' => 
  array (
    'content_id_4' => NULL,
    'content_id_5' => NULL,
  ),
  'Test Parent&gt;Test Child&gt;Test Sub Child' => 
  array (
    'content_id_3' => NULL,
  ),
  'Test Parent 2 with No Kids' => 
  array (
    'content_id_3' => NULL,
  ),
  'Collections&gt;Sports' => 
  array (
    'content_id_2' => NULL,
    'content_id_22' => NULL,
  ),
  'Collections' => 
  array (
    'content_id_2' => NULL,
    'content_id_22' => NULL,
    'content_id_6' => NULL,
  ),
  'Collections&gt;Charity' => 
  array (
    'content_id_6' => NULL,
  ),
)

In the above example, Test Parent>Test Child>Test Sub Child would mean that there is a parent category Test Parent that has a child Test Child. Test Child also is a parent and has a child called Test Sub Child that does not have any children.

Example output required:

array (
  'Collections' => 
  array (
    'Sports' => NULL,
    'Charity' => NULL,
  ),
  'Test Parent' => 
  array (
    'Test Child' => 
    array (
      'Test Sub Child' => NULL,
    ),
  ),
  'Test Parent 2 with No kids' => NULL,
  'Study' => 
  array (
    'Study Groups' => NULL,
  ),
)

I attempted a solution but can't manage to get the syntax right so that I can create an additional array with a child's children.

I don't necessarily require my example to be refactored. I am simply looking for the best solution that works.

My example code

$category_structure = array();
foreach($event_categories as $main_cat => $content_ids) {

    $this_category_list = explode('&gt;', $main_cat);

    $this_cat = array();
    $this_parent = array_shift($this_category_list);


    foreach($this_category_list as $cat) {
        $this_cat[$this_parent][$cat] = null;
    }

    $category_structure = array_merge_recursive($this_cat, $category_structure);


}

Instead of posting a var_dump() of your array, consider posting a var_export() of it instead. — nickb
– nickb, Commented Jul 22, 2015 at 12:41
can you show the code, where this array is coming from? there must be something that can make this easy. @DaveO'Dwyer — Viral
– Viral, Commented Jul 22, 2015 at 13:30
@Viral The source array is coming from a CMS - I have no control over its data structure. — Dave O'Dwyer
– Dave O'Dwyer, Commented Jul 22, 2015 at 19:46

DavidDomain · Accepted Answer · 2015-07-23 00:39:54Z

2

This should work for you, making sure there are no zero indexed items in the result. Which comes from array_merge_recursive i think, by merging the null valued item to the ones that have an associative key.

It is not as elegant as P0rnflake's solution though, but i am sure you will get the idea.

$collect = array();
$result = array();
$last = "";
foreach($event_categories as $main_cat => $content_ids) {
    if (strpos($last, $main_cat) === false) {
        array_push($collect, explode('&gt;', $main_cat));
    }
    $last = $main_cat;
} 
array_walk($collect, function($value) use (&$result) {
    $out = array();
    $cur = &$out;
    foreach ($value as $array) {
        if (count($value) !== 1) {
            $cur[$array] = array();
        } else {
            $cur[$array] = null;    
        }
        $cur = &$cur[$array];
    }
    $cur = null;
    $result = array_merge_recursive($result, $out);
});
var_dump($result);

edited Jul 23, 2015 at 0:39

answered Jul 22, 2015 at 16:35

DavidDomain

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2 Comments

Dave O'Dwyer Over a year ago

Thank you Dave. Very much appreciated. This is working exactly as expected.

DavidDomain Over a year ago

Sure, happy coding! ;-)

NiMeDia · Accepted Answer · 2015-07-29 07:56:58Z

1

This solution should work on php >= 5.3.0 ($yourArray is the input array):

// anonymous recursive function which merges a flat numeric array 
// into a hierarchy, f.e. array('parent','child','grandchild')
// will be built to a hierarchical array
$treeBuilder = function($numArray) use (&$treeBuilder) {
    if(isset($numArray[1])) {
        //recursive merge needed, there are still entries left
        return array(
            $numArray[0] => $treeBuilder(array_slice($numArray, 1))
        );
    }
    //end is reached
    return array(
        $numArray[0] => null
    );
};

$result = array();
foreach (array_keys($yourArray) as $key) {
    // loop through exploded keys and merge results
    $hierarchy = explode('&gt;', $key);
    $result = array_merge_recursive($result, $treeBuilder($hierarchy));
}
var_dump($result);

edited Jul 29, 2015 at 7:56

answered Jul 22, 2015 at 13:49

NiMeDia

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2 Comments

Dave O'Dwyer Over a year ago

Thank you for your attempt at this. Resulting array structure looks to fit perfectly apart from a key 0 with a value of null existing in all returned arrays. It appears to be coming from code return array( $numArray[0] => null

NiMeDia Over a year ago

ye, you are right, I think this happens from the 'Collections' entry without separator

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