Recursive function adds data to existing string?

Hi guys! I'm new here!

I have a problem that I can't solve, no matter how hard I try. Maybe you can help me?

I have an array and a function to create a multi-level menu out of this array. Array is not multi-level. The problem: when I echo in function, everything works fine, but when I try to add all data to a string (to return it later), it doesn't add strings that have been created by recursion.

Code

Array structure:

$menu[$row['id']] = array('title' => $row['title'], 'app' => $row['app'], 'parent' => $row['parent'], 'position' => $row['position']);

Code (markup):

$menu = html_menu($menu(array), $parent(parent's id), $active(some id), $multilevel(one-level vs multi), $html = ''(empty container));

Function:

function html_menu($data, $parent, $active,  $multilevel, $html) { 
		
	foreach($data as $key => $value) {
	
		if($data[$key]['parent'] == $parent) {
			
			$activate = ($key == $active ? 'class="active"' : "");
			$title = $data[$key]['title'];
			
			$html .= "<li>\n<a href=\"".MODULEURL.$data[$key]['app']."/index.php?action=open&amp;id=".$key."\"".$activate.">".$title."</a>\n";
			
			if($multilevel) html_menu($data, $key, $active, $multilevel, $html);
			
			$html .= "\n</li>\n"; 
		}
	}
	
	return $html;
}

Code (markup):

I hope you understand what I'm trying to do

Please do not tell me to query recursively from mysql, cause it takes wayyyyyyyyy longer

Thanks guys!

 

Try this one

function html_menu($data, $parent, $active,  $multilevel, $html) { 
		
	foreach($data as $key => $value) {
	
		if($data[$key]['parent'] == $parent) {
			
			$activate = ($key == $active ? 'class="active"' : "");
			$title = $data[$key]['title'];
			
			$html .= "<li>\n<a href=\"".MODULEURL.$data[$key]['app']."/index.php?action=open&amp;id=".$key."\"".$activate.">".$title."</a>\n";
			
			if($multilevel) { 
                           $html .= html_menu($data, $key, $active, $multilevel, $html);
                        }
			
			$html .= "\n</li>\n"; 
		}
	}
	
	return $html;
}

Code (markup):

 

Nothing happens, sorry

 

can you paste the code when you actually call the function and how you try to display the result of the function?

 

on page:
$sidebar['left'][0] = get_menu(false, $id , true);

That calls out a function that gets all the results from DB and creates a non-multi-level array and passes it to the function above. That function returns the output (html formatted string), first function returns the string to sidebar['left'].

The problem: recursive part of the function does not add created string to another string (i think .= does not work or something). Why I think that? Cause when switch $html .= "blah"; to echo "blah"; everything works.

So --- wtf id going on with .= when function recursives itself?

Thanks for helping