php无限极分类

<?php
$conn = mysql_connect("localhost","root","1234");
mysql_select_db("laaho_caike");

$option = getTree(0);
$option = "<select name='term'>" . $option . "</select>";
echo $option;

function getTree($id,$spac=0) {
//static $str;
$spac = $spac + 2;
static $str;
$sql = "select * from videoterm where parent_id='" . $id . "'";
$res = mysql_query($sql);
//$arr = mysqli_fetch_assoc($res);

while ($arr=mysql_fetch_assoc($res)) {
$str .= "<option value=" . $arr['Id'] . ">" . str_repeat(' ',$spac) . "|--" . $arr['termname'] . "</option>";
getTree($arr['Id'],$spac);

}

return $str;
}
?>