PHP header 有关问题

PHP header 问题
代码如下 一直出现 Warning: Cannot modify header information - headers already sent by (output started at D:AppServwwwadmin_check.php:1) in D:AppServwwwadmin_check.php on line 10

  require_once 'user_service.class.php';

$admin_id=$_POST['admin_id'];
$admin_password=$_POST['admin_password'];

$userService=new userservice();
if($name=$userService->checkUser($admin_id, $admin_password)){

header("Location: manage.php?name=$admin_id");

exit;
}else{

header("Location: login.php?error=1");
exit;

}
?>这段代码前端没有问题 都是执行到header 出现的问题
这是user_service.class.php
require_once 'sqlhelper.class.php';
require_once 'user.class.php';
class userservice{


//提供一个根据用户名name获取一个账号信息的方法
public function getUserByName($name) {

$sql="select * from user where name='".$name."'";

$sqlHelper= new sqlhelper();

$arr=$sqlHelper->dql2($sql);

$sqlHelper->close_conn();

return $arr;//
}
//提供一个验证用户是否合法的方法

public function checkUser($name,$password){


$sql="select password ,name from user where name='".$name."'";
//创建一个sqlhelper对象
$sqlHelper=new sqlhelper();
$res=$sqlHelper->dql($sql);
if($row=mysql_fetch_assoc($res)){
//比对密码
if($password==$row['password']){
return $row['name'];

}

}
mysql_free_result($res);
$sqlHelper->close_conn();
return "";
}
public function gengGPassword($name,$newpassword){

$sql="update user set password='".$newpassword."' where name='".$name."'";

$sqlHelper=new sqlhelper();

$res=$sqlHelper->dql($sql);

// mysql_free_result($res);
$sqlHelper->close_conn();
}
}
?>
sqlhelper.class.php代码
//工具类
class sqlhelper{

public $host="localhost";
public $user="root";
public $password="123456";
public $db="bishe";
public $conn;
public function sqlhelper(){

$this->conn=mysql_connect("localhost","root","123456") or die ("123".mysql_errno () );

if(!$this->conn){
die("连接失败".mysql_errno());
}
mysql_query("set names utf8");
mysql_select_db($this->db,$this->conn);

}

public function dql($sql){

$res=mysql_query($sql,$this->conn)or die(mysql_errno());

return $res;
}
public function dql2($sql){

$res=mysql_query($sql,$this->conn)or die("错误！".mysql_errno());

$arr=mysql_fetch_array($res,$this->conn);
return $arr;
/* echo $arr[0],$arr['1'];
$result = mysql_query("SELECT * from user where name='xiaowang'");

  while ($row = mysql_fetch_array($result, MYSQL_NUM)) {
  printf ("ID: %s Name: %s", $row[0], $row[1]);
  }

  mysql_free_result($result);
return $row;*/
}
//public function dql2($sql){
// $res=mysql_query($sql,$this->conn)or die(mysql_errno());

//return $res;
//}
//删除？
public function dml($sql){
$b=mysql_query($sql,$this->conn);
if (!$b) {
return 0;//失败
;
}else {
if (mysql_affected_rows($this->conn)>0){
return 1;//表示执行OK
}else {
return 2;//表示没有行收到影响
}
}

}


public function close_conn(){