Using recursion to build navigation

Question

I\'m building navigation for a site and for the life of me I can\'t figure out recursion. I have all my data stored via MySQL using this design:

Answer 1

Here's an example with recursion.

function buildNavigation($items, $parent = NULL)
{
    $hasChildren = false;
    $outputHtml = '
%s
';
    $childrenHtml = '';

    foreach($items as $item)
    {
        if ($item['parent'] == $parent) {
            $hasChildren = true;
            $childrenHtml .= '
'.$item['category_name'];         
            $childrenHtml .= buildNavigation($items, $item['category_id']);         
            $childrenHtml .= '
';           
        }
    }

    // Without children, we do not need the 
 tag.
    if (!$hasChildren) {
        $outputHtml = '';
    }

    // Returns the HTML
    return sprintf($outputHtml, $childrenHtml);
}

print buildNavigation($items);

That script produces the following output :

    
Menu 1
    
Menu 2
        

            
Sub Menu 2.1
            
Sub Menu 2.2
            
Sub Menu 2.3
                

                    
Sub Menu 2.2.1
                    
Sub Menu 2.2.2
                    
Sub Menu 2.2.3
                
            
        
    
    
Menu 3