using bootstrap css

array_tree_v2.php

<?php
function buildtree(&$result,$dropdown,$space='',$callback=null){
    $drop = false;
    if(!is_array($dropdown) || count($dropdown) < 1 ){ return false; }
    $i = 0;
    $space .= $space;
    while($i < count($dropdown)){
        $key        = key($dropdown);
        $item       = ( is_numeric($key) ? $dropdown[$key] : $key );
        $childexist = !empty($dropdown[$item]) && is_array($dropdown[$item]);
        if(is_callable($callback)){
            $result .= $callback($item,$childexist,$space);
        }
        
        if($childexist){//exist child array
            $result .= '<div class="panel list-sub">
                        <div class="panel-body">
                          <div class="list-group">';
        }
        if(is_array($dropdown[$key])){
            buildtree($result,$dropdown[$key],$space,$callback);
        }
        if($childexist){//exist child array
            $result .= '</div>
                     </div>
                  </div>';
        }
        next($dropdown);
        $i++;
    }
} 
/*$dropdowns = array(
    'category' => array(
        'men'=>array('departments','designers','surf by price','surf by size'=>array('one','two'=>array('one','two','three','four'),'three','four')),
        'women'=>array('departments','designers','surf by price','surf by size'),
        'handbags'=>array('styles','designers','surf by price','surf by material')
    ),
    'condition' => array(),
    'size'      => array(),
    'Brand'     => array(),
    'Pricing'   => array()
);*/
$result = '';
$space = '&nbsp;';
buildtree($result,$dropdowns,$space,function($item,$childexist,$space){
    return '<a href="#" class="list-group-item"><span>'.$space.$item.'</span>'.
    ( $childexist ? '<span class="glyphicon glyphicon-menu-right mg-icon pull-right"></span>' : '' ).
    '</a>';
});
?>
<div class="row">
<div class="col-lg-10 col-lg-offset-1 col-md-10 col-md-offset-1 col-sm-10 col-sm-offset-1">
 <div class="panel panel-default">
    <div class="panel-body">
      <div class="slide-container">
        <div class="list-group" id="mg-multisidetabs">
            <?php echo $result; ?>
        </div><!-- ./ end list-group -->
      </div><!-- ./ end slide-container -->
    </div><!-- ./ end panel-body -->
  </div><!-- ./ end panel panel-default-->
</div><!-- ./ endcol-lg-6 col-lg-offset-3 -->
</div><!-- ./ end row -->