Recursive function with unknown depth of values. Return all values (undefined depth)

Question

I have a question about a recursive PHP function. I have an array of ID’s and a function, returning an array of „child id’s“ for the given id.

public function getChildId($id) {
    …
    //do some stuff in db
    …
    return childids;
}

One childid can have childids, too! Now, I want to have an recursive function, collecting all the childids.

I have an array with ids like this:

$myIds = array("1111“,"2222“,"3333“,“4444“,…);

and a funktion:

function getAll($myIds) {

}

What I want: I want an array, containing all the id’s (including an unknown level of childids) on the same level of my array. As long as the getChildId($id)-function is returning ID’s…

I started with my function like this:

function getAll($myIds) {
    $allIds = $myIds;
    foreach($myIds as $mId) {
        $childids = getChildId($mId);

        foreach($childids as $sId) {
            array_push($allIds, $sId);

            //here is my problem.
            //what do I have to do, to make this function rekursive to
            //search for all the childids? 

        }       
    }
    return $allIds;

}

I tried a lot of things, but nothing worked. Can you help me?

in your current example, $myIds is a simple flat array, maybe you could add a proper sample — user1978142
– user1978142, Commented Jun 6, 2014 at 14:42
Can you put up a better example of your array on which this function has to run? The current one is just a simple one dimensional array with no depth. — Hanky Panky
– Hanky Panky, Commented Jun 6, 2014 at 14:42
$myIds is my array with the given "root"-Ids. From these Ids, I want to search all the child Id's (my function getChildId()) looks in a table in my database for a dataset having the given Id as primary key, so it is a relation to the root id. In my database one "id" can have many child id's and one child id, can have many child ids, too (and so on)) — Newbie
– Newbie, Commented Jun 6, 2014 at 14:52

halabuda · Accepted Answer · 2014-06-06 15:40:45Z

1

Assuming a flat array as in your example, you simply need to call a function that checks each array element to determine if its an array. If it is, the function calls it itself, if not the array element is appended to a result array. Here's an example:

$foo = array(1,2,3,
  array(4,5,
    array(6,7,
      array(8,9,10)
    )
  ),
  11,12
);

$bar = array();
recurse($foo,$bar);

function recurse($a,&$bar){
  foreach($a as $e){
    if(is_array($e)){
      recurse($e,$bar);
    }else{
      $bar[] = $e;
    }
  }
}

var_dump($bar);

DEMO

edited Jun 6, 2014 at 15:40

answered Jun 6, 2014 at 15:08

halabuda

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1 Comment

MrGlass Over a year ago

You need to read the example more carefully. He is not storing all the sub IDs in nested arrays. Instead he has a function to lookup from a DB

MrGlass · Accepted Answer · 2014-06-06 14:51:10Z

0

I think this code should do the trick

function getAll($myIds) {
    $allIds = Array();
    foreach($myIds as $mId) {
        array_push($allIds, $mId);
        $subids = getSubId($mId);

        foreach($subids as $sId) {
            $nestedIds = getAll($sId);
            $allIds = array_merge($allIds, $nestedIds);
        }       
    }
    return $allIds;
}

answered Jun 6, 2014 at 14:51

MrGlass

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5 Comments

Ben Fortune Over a year ago

You should add checks to see if it's still an array, otherwise it's going to produce errors.

halabuda Over a year ago

where is getSubId() defined?

Newbie Over a year ago

Thank you very much! This solution helped me a lot! @halabuda: I changed getSubId to getChildId for a better understanding of my problem.

MrGlass Over a year ago

@halabuda sorry, i renamed getChildIds to getSubIds. Hadn't had my morning caffeine yet

MrGlass Over a year ago

@BenFortune Yeah, this is a bit sketchy in that regard, but I was trying to keep close to the question to make it easier to understand. Ideally I would rearrange this so that getSubId is the recursive function, and require that it always be fed 1 ID

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