// use...
$CATEGORIES = Category::GetCategoriesTree();
echo CreateMenuTree( $CATEGORIES );

// function...
function CreateMenuTree( $CATEGORIES ){
    
    ob_start();
    
    echo '<ul>';
    
    foreach( $CATEGORIES as $Category ){
        echo '<li>';
        echo '<a>' . $Category[ 'NAME' ] . '</a>';
        
        if ( is_array( $Category[ 'CHILDREN' ] ) ){
            echo CreateMenuTree( $Category[ 'CHILDREN' ] );
        }
        
        echo '</li>';
    }
    
    echo '</ul>';
    
    $result = ob_get_contents();
    ob_end_clean();
    
    return $result;
    
}