Creating a toggleable treeview with PHP and jQuery

cloud
    candidates
        one
            one1.xls
            one2.pdf
        three
        two
            a
            two
                info.txt
            info.txt
        info.rtf
        logo.jpg
        readme.txt
    clients
        one
            one
            one1.txt
            one2.png
            one3.doc
            one4.docx
        two
            two1.rtf
        readme.txt
    employees
        index.php
        .htaccess

class TreeView
{
    private $root;

    public function __construct($path)
    {
        $this->root = $path;
    }

    public function getTree()
    {
        return $this->createStructure($this->root, true);
    }

    private function createStructure($directory, $root)
    {
        $structure = $root ? '<ul class="treeview">' : '<ul>';

        $nodes = $this->getNodes($directory);
        foreach ($nodes as $node) {
            $path = $directory.'/'.$node;
            if (is_dir($path) ) {
                $structure .= '<li class="treeview-folder">';
                $structure .= '<span>'.$node.'</span>';
                $structure .= self::createStructure($path, false);
                $structure .= '</li>';
            } else {
                $path = str_replace($this->root.'/', null, $path);
                $structure .= '<li class="treeview-file">';
                $structure .= '<a href="download_cloud.php?'.$path.'">'.$node.'</a>';
                $structure .= '</li>';
            }
        }

        return $structure.'</ul>';
    }

    private function getNodes($directory = null)
    {
        $folders = [];
        $files = [];

        $nodes = scandir($directory);
        foreach ($nodes as $node) {
            if (!$this->exclude($node)) {
                if (is_dir($directory.'/'.$node)) {
                    $folders[] = $node;
                } else {
                    $files[] = $node;
                }
            }
        }

        return array_merge($folders, $files);
    }

    private function exclude($filename)
    {
        return in_array($filename, ['.', '..', 'index.php', '.htaccess', '.DS_Store']);
    }
}

$treeView = new TreeView('cloud');
echo $treeView->getTree();

$(document).ready(function() {
    $('.treeview').find('ul').hide();

    $('.treeview-folder span').click(function() {
        $(this).parent().find('ul:first').toggle('medium');

        if ($(this).parent().attr('className') == 'treeview-folder') {
            return;
        }
    });
});

.treeview span:hover {
    cursor: pointer;
}
.treeview-folder {
    list-style-image: url('../images/icon_folder.png');
}
.treeview-file {
    list-style-image: url('../images/icon_file.png');
}