recursion - returns sometimes

[cgraz]

I have a recursive function that loops through an array. The function only returns $value (my result) sometimes, but the times that the function just returns NULL, i go in and print $value in the function and it's set to the correct value. i've printed out my key value/pairs in the recursive loop and the recursion is occuring properly as far as I can see. Here's my array:

Array
(
    [index] => index
    [company] => Array
        (
            [careers] => careers
            [contact] => contact
        )

[solutions] => Array
    (
        [information-technology] => Array
            (
                [business-processes] => business-processes
                [network-strategy] => network-strategy
                [virtual-private-networks-vpns] => virtual-private-networks-vpns
                [network-security] => network-security
                [disaster-recovery] => disaster-recovery
            )

        [site-development] => Array
            (
                [internet-strategies] => internet-strategies
                [web-sites] => web-sites
                [intranets] => intranets
                [content-management] => content-management
            )

    )

[process] => process
[case-studies] => case-studies
[get-started] => get-started
) 

Here's the function:

	function grabChildren( $vals = array() )
	{
		if(count($vals) == 0) 
		{
			$vals = $GLOBALS['menu']->tree;
		}

	foreach($vals as $key => $value)
	{
		if($key == $this->id)
		{
			return $value;
		}
		else
		{
			if(is_array($value) )
			{
				$this->grabChildren( $value );
			}
		}
	}
}

And here's how I call it:

// parameter 1 here (solutions) is $this->id in my class, and it holds the proper value
$item = new menuItem('solutions', 'Solutions');

$children = $item->grabChildren();

print_r($children);

When I use solutions, company, process (the first key/vals in the array) as my first parameter, it returns fine. When I use anything in the second level (information-technology, site-development), it returns null. But i print $value in my function and the result is always correct (returns an array of children).

I also tried changing return $value to $this->children = $value; and when I print $item->children it always works. I need the function to return the value however, so this isnt' an option.

There are no empty values, the loops all work, it holds the variable to return, it just won't return. I've even tried

$return = $value; then doing

return $return; on the last line of the function and still nothing. But print_r($return) and i see the result.

Anyone have any ideas what I'm doing wrong here?

[jdorsch]

You never return $this->grabChildren($value) on the recursive call, so if it goes deeper the method will return null. When you are in a recursive function and call return, the return goes to the parent caller, so if you call grabChildren() from grabChildren(), the calling grabChildren() must return the internal grabChildren(). Confused yet?

And what in the H is this: $GLOBALS['menu']->tree?

Also, iterators are your friend, learn to love them

foreach( 
   new RecursiveIteratorIterator( 
     new RecursiveArrayIterator( $treeArray ), 
         RecursiveIteratorIterator::SELF_FIRST ) as $key => $value )
{
  if( $key == $this->id ) return $value ;
}

[cgraz]

crazy. never heard/seen that iterator stuff 😉

I must've forgot to mention in my post that i originally had a call to return before i recurse, but that makes it return only on company (which is even less than without it) so i took it out.

$GLOBALS['menu']->tree is the navigational tree (from my earlier post) held in object $menu. I'm developing a framework, so it's all in the navigation/menu package.

The iterator code you gave me returns this error:

Parse error: parse error, unexpected ')', expecting '(' in /home/ixpleoco/public_html/ix/lib/Menu/MenuItem.php on line 41

referring to this ending parenthesis: RecursiveIteratorIterator::SELF_FIRST)

I've never used this before, so I'm not exactly sure what it might be? The function looks like this:

	function grabChildren( $vals = array() )
	{
		foreach(new RecursiveIteratorIterator(new RecursiveArrayIterator
				( $GLOBALS['menu']->tree ), 
					RecursiveIteratorIterator::SELF_FIRST) 
						as $key => $value )
		{
			if( $key == $this->id ) 
			{
				return $value ;
			}
		}
}

Is there also a reason why even when I call return before the recursion call, it still isn't returning (and actually only returns on company).

Thanks for all your help.

[jdorsch]

The error might be caused to the version of PHP you are using. The SELF_FIRST constant format was changed recently. What version are you running?

Your existing method must be changed with a return at grabchildren otherwise anything beyond 1 level deep will return Null.

1 level deep

GrabChildren
returns $value

2 levels deep

GrabChildren1 <-- returns nothing
GrabChildren2
returns $value to GrabChildren1

3 levels deep

GrabChildren1 <-- returns nothing
GrabChildren2 <-- returns nothing
GrabChildren3
returns $value to GrabChildren2

How it should work
GrabChildren1 <-- returns $value to original caller
GrabChildren2 <-- returns $value to GrabChildren1
GrabChildren3
returns $value to GrabChildren2

So if its 3 levels deep $value gets returned 3 times, up through each caller in the recursive structure

function grabChildren( $vals = array() )
    {
        if(count($vals) == 0)
        {
            $vals = $GLOBALS['menu']->tree;
        }

    foreach($vals as $key => $value)
    {
        if($key == $this->id)
        {
            return $value;
        }
        else
        {
            if(is_array($value) )
            {
                // This must be changed
                return $this->grabChildren( $value );
            }
        }
    }
} 

[cgraz]

I understand the return before the recursive call, what's odd is that actually makes it worse (which is why I removed it originally).

For example, on a search for $id 'information-technology', printing the key-value pairs while calling return $this->getChildren(....) returns

index - index
company - Array
careers - careers
contact - contact

(leaves out solutions for some reason)

and $value is null when I print within function.

Removing the return and just calling $this->getChildren(...) returns the following:

index - index
company - Array
careers - careers
contact - contact
solutions - Array
information-technology - Array ($value holds the array here when I print, just doesn't return it)
process - process
case-studies - case-studies
get-started - get-started

I'm not sure what I'm missing here.

oh, and PHP Version 4.4.1

[cgraz]

Got it! Here's the function if you're interested

	function grabChildren( $vals = array() )
	{
		if(count($vals) == 0) 
		{
			$vals = $GLOBALS['menu']->tree;
		}

	foreach($vals as $key => $value)
	{
		if($key == $this->id)
		{
			$ret = $value;
			break;
		}
		else
		{
			if(is_array($value))
			{
				$ret = array_merge($ret, $this->grabChildren( $value ));
			}
		}
	}

	return (is_array($ret)) ? $ret : false;
}

Works beautifully down to as many levels as I have (I added levels in different places, new pages, etc). Thanks for all your help with this and the tree.