Why doesn't this PHP recursive function return the value?

Question

I was working on an API for ustream which returns the following array

Array
(
[results] => Array
    (
        [0] => Array
            (
                 


        

Answer 1

You're not doing anything with the return from your recursion call. It's a bit more complex than simply returning it, because you only want to cascade out if we actually found anything.

Try this:

function recursion($array) {
    foreach ($array as $key => $value) {
        if($key==='sourceChannel') {
            return $value['id'];
        }
        if (is_array($value)) {
            $rc = recursion($value);
            if (!is_null($rc)) return $rc;
        }
    }
    return null;
}

First, I added return null; to the end of the function - if we didn't find anything, we return null.

Then, when I recurse, I check the return value... if it's non-null, it means we found something and we want to return it. If it is null, we don't want to return - we want to continue the loop instead.

Answer 2

You could use iterators to make your function a whole lot easier:

function findSourceChannel($array)
{
    foreach (new RecursiveIteratorIterator(new RecursiveArrayIterator($array)) as $key => $value) {
        if ($key == 'sourceChannel') {
            return $value['id'];
        }
    }
    return null;
}

That said, I'm not sure why you can't just do a search like this:

foreach ($array['results'] as $result) {
    if (isset($result['sourceChannel'])) {
        return $result['sourceChannel']['id'];
    }
}
return null;

Answer 3

Your code is flawed because you need to change

recursion($value);

into

return recursion($value);

The return will take the answer back to the caller until the first caller is reached.

edit: The lesson here is that your function should ALWAYS return a value. So here is some more elaboration:

function recursion($array) {
    if (!is_array($array)) // check if what you're getting is an array!
        return null;
    foreach ($array as $key => $value) {
        if($key==='sourceChannel') {
            return $value['id'];
        }
        if (is_array($value)) {
            $result = recursion($value);
            if ($result !== null) {
                return $result;
            }
        }
    }
    return null; // this happens if all recursions are done and sourceChannel was not found
}

Answer 4

Try like this

foreach ($array['results'] as $key => $value) {
   if($key == "sourceChannel"){
        $getId = $value['id'];
        //print_r($getId);
        return $getId;
   }       
}