Multi level selectbox

Question

I have a problem with building multi level select box. I have category table with structure: id, parent_id, name. If parent_id = 0 it is top level. i don't know level depth, so it could be 2,3-5 levels. How i can build it with on query "SELECT * FROM cats" Result suppose to look like

<select>
<option>cat_name</option>
<option>--cat_name_l1</option>
<option>--cat_name_l1</option>
<option>----cat_name_l2</option>
<option>----cat_name_l2</option>
<option>cat_name</option>
</select>  

Can You help me?

Answer 1

function _buildTree($data, $idParent, $indentSymbol, $level)
{
    $cat = array();
    foreach($data as $row){
        if($row['parent_id'] == $idParent){
            if($indentSymbol AND $level > 0){
                $symbols = array_fill(0, $level, $indentSymbol);
                $cat[$row['id']] = implode('', $symbols) . $row['name'];
            }else{
                $cat[$row['id']] = $row['name'];
            }

            $cat = $cat + _buildTree($data, $row['id'], $indentSymbol, $level++);
        }
    }
    return $cat;
}

$result = mysql_query("SELECT * FROM cats");

$data = array();
while($row = mysql_fetch_assoc($result)){
    $data[] = $row;
}

$select = '<select>';

foreach(_buildTree($data, 0, '-', 0) as $key=>$option){
    $select .= '<option value=' . $key . '>' . $option . '</option>';
}

$select .= '</select>';

Answer 2

Try this for generating the required dropdown:

$result=mysql_query("SELECT * FROM cats");
$opt='<select>';
while($row=mysql_fetch_array($result))
{
    $cat[$row['id']][0]=$row['parent_id'];
    $cat[$row['id']][1]=$row['name'];
}
foreach($cat as $ct)
{
    $level=0;
    $temp=$ct;
    while($temp[0]!=0)
    {
        $temp=$cat[$temp[0]];
        $level++;
    }
    $opt.="<option>";
    for($i=0;$i<$level;$i++)
    {
        $opt.="--";
    }
    $opt.=$ct[1];
    $opt.="</option>";
}
$opt.="</select>";

Then, you can use this as:

echo $opt;