a sample to make a tree by php

SQL code
CREATE TABLE `tree` (
  `id` int(11) NOT NULL,
  `name` varchar(255) collate utf8_bin NOT NULL,
  `parent` int(11) NOT NULL,
  `ischild` int(11) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

PHP code
mysql_connect('localhost', 'root', '123456');
mysql_select_db("wz");
mysql_query("set names 'utf8'");
//获得顶节点
$sql = "select id, name,ischild from tree where parent = 0 order by id asc";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
    extract($row);

    $icon = $ischild ? "javascript:expand(\"div$id\");'>+":"-";
    $name = $icon . $name;
    echo "

" . $name;
    if($ischild)
    {    
        getNode($id, 0);
    }
    echo "

";
}
function getNode($id, $level)
{
    $sql = "select id, name, ischild from tree where parent = $id order by id asc ";
    $result = mysql_query($sql);
    $level++;
  while($row = mysql_fetch_array($result))
  {
      extract($row);
        $icon = $ischild ? "+":"-";
        $name = $icon . $name;  
        echo "

" . echoChar("    ", $level)  . $name;
        if($ischild)
        {
            getNode($id, $level);
        }
        echo "

";
  }
}
function echoChar($char, $num)
{
    for($i=0;$i< $num; $i++)     {         $strChar .= $char;     }     return $strChar; } ?>