Php function not returning array values

Question

Sorry for this dumb question, but I really don't see what I'm doing wrong :(

I've this 2 functions within a class

function getParentCat($treeTag) 
{

    // fetch some db data
    $parentId = $row->Fparent_id;
    $parentArray = array();

    if ($parentId > 0) {
        $parentArray = $this->iterateParentCat($parentArray,$parentId);

            // print_r here show nothing, no array, nothing !

    }  else {
        $parentArray[] = $treeTag;
    }
    return $parentArray;
}

And the second function :

function iterateParentCat($parentArray,$parentId)
{
    // Fetch some db data
    $parentArray[] = $row->Ftag;

    if ($row->Fparent_id > 0) {
        $this->iterateParentCat($parentArray,$row->Fparent_id);

    }  else {

         // print_r here show a perfect, beautiful array

        return $parentArray;
    }
}

So it seems I've lost the array (not just the content, the whole array) between the 2 functions. It must be a simple thing... but I can't see it ! Soooory :)

return $this->iterateParentCat($parentArray,$row->Fparent_id);? — u_mulder
– u_mulder, Commented Apr 1, 2020 at 8:44
Thank you !!! I knew it was something really obvious ! My mind is fogged... a 1000 thanks ! — Siouw
– Siouw, Commented Apr 1, 2020 at 8:50

Hassan Nasir · Accepted Answer · 2020-04-01 09:05:31Z

3

Create reference variable.

function getParentCat($treeTag) 
    {

        // fetch some db data
        $parentId = $row->Fparent_id;
        $parentArray = array();

        if ($parentId > 0) {
            $parentArray = $this->iterateParentCat(&$parentArray,$parentId);

                // print_r here show nothing, no array, nothing !

        }  else {
            $parentArray[] = $treeTag;
        }
        return $parentArray;
    }

answered Apr 1, 2020 at 9:05

Hassan Nasir

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Comments

Martijn · Accepted Answer · 2020-04-01 08:51:09Z

You are using recursive logic (calling itself to go deeper), but you do nothing with the result you get from it. Every call you go deeper, the $parentArray from the one-level-up doesn't exists. So it adds values to the array, returns it, but then the one-upper does nothing with it :)

function iterateParentCat($parentId)
{
    // Fetch some db data
    $data = [$row->Ftag];

    if ($row->Fparent_id > 0) {
        $recursiveData = $this->iterateParentCat($row->Fparent_id);
        $data = array_merge($data, $recursiveData); // add the data from one down (and one down (and one down))
    }

    return $data;
}

Alternatively, you could do iterateParentCat(&$parentArray,$parentId), telling php that the while recursive path now worth by reference, they will now will update the same variable. IMO this isn't the way go, by-reference should be avoided if you can as it can make simple thing very complex, very fast.

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