array_tree.php

<?php
function buildtree(&$result,$dropdown,$space=' ',$bool=true){
    if(!is_array($dropdown) || count($dropdown) < 1 ){ return false; }
    $i = 0;
    $space .= $bool ? $space : '';
    while($i < count($dropdown)){
        $key = key($dropdown);
        $result .= $space;
        $result .= ( is_numeric($key) ? $dropdown[$key] : $key );
        $result .= '<br />';
        if(is_array($dropdown[$key])){
            buildtree($result,$dropdown[$key],$space);
        }
        next($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 = '';
$space  = '-';
buildtree($result,$dropdowns,$space);
echo $result;
/*
    --category
    ----men
    --------departments
    --------designers
    --------surf by price
    --------surf by size
    ----------------one
    ----------------two
    --------------------------------one
    --------------------------------two
    --------------------------------three
    --------------------------------four
    ----------------three
    ----------------four
    ----women
    --------departments
    --------designers
    --------surf by price
    --------surf by size
    ----handbags
    --------styles
    --------designers
    --------surf by price
    --------surf by material
    --condition
    --size
    --Brand
    --Pricing
*/
?>

array_tree_with_ul.php

<?php
function buildtree(&$result,$dropdown,$space=' ',$callback,$bool=true){
    if(!is_array($dropdown) || count($dropdown) < 1 ){ return false; }
    $i = 0;
    $space .= $bool ? $space : '';
    while($i < count($dropdown)){
        $key = key($dropdown);
        $result .= '<ul>';
        $item = ( is_numeric($key) ? $dropdown[$key] : $key );
        if(is_callable($callback)){
            $result .= $callback($item,$space);
        }
        if(is_array($dropdown[$key])){
            buildtree($result,$dropdown[$key],$space,$callback);
        }
        $result .= '</ul>';
        next($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($item,$space){
    return '<li>'.$item.'</li>';
});
echo $result;