<?
include("includes/config.php");
//第 7,8 行报错
lei(0);
$ii=0;
function lei($belongs_id){

// 解决方法1, 不填$conn
$sql=mysql_query("select * from pro_type where belongs_id='".$belongs_id."'");
// 解决方法2, 以参数传递，或声明为全局
// global $conn;
// $sql=mysql_query("select * from pro_type where belongs_id='".$belongs_id."'", $conn);


while($rs_info=mysql_fetch_array($sql)){
//大类
if($belongs_id==0){
echo "大类";
}else{
echo "小类";
}
$ii=$ii+1;
lei($rs_info["id"]);
$ii=$ii-1;
}
}
?>

------解决方案--------------------
难道要
global $conn ;
$sql=mysql_query("select * from pro_type where belongs_id='".$belongs_id."'",$conn);