Infinite-level classification implemented by php and mysql | tree display classification relationship

//$count is the classification level
sort_list($str,$fatherid,$count)
{
$rs = $this->sql->re_datas("select * from sort where father_id = fatherid");
$num = $this->sql->sql_numrows();
$i=0;
$n = 1;
while(isset($rs[$i]))
{
$name = "";
for($n = 1 ; $n < $count ; $n++)
{
$name.="│ ";
}
if($i+1==$ num)
{
$name.="└─".$rs[$i][name];
}
else
{
$name.="├─".$rs[$i][name];
}
if($rs[$i][isdir])
{
$str.="".$name."";
 }
else
{
$str.=$name";
}
$temp = $count+1;
$str = $this->sort_list($str,$rs[$i][id],$ temp);
$i++;
}
return $str;
}
?>

where $this->sql object is a sql operation class object, and the re_datas() function returns the found Array, sql_numrows() function returns the queried number Calling method: $sort_list = sort_list($sort_list,0,1);