我正在建立一个学生的结果门户网站，我希望每个引脚一个学生的5倍。这是我的密码：

if (!$error) {
    $res=mysql_query("SELECT * from pin WHERE userid='$reg'");
    $row=mysql_fetch_array($res);
    $count = mysql_num_rows($res); // if regno correct it returns must be 1 row
    if( $count == 1 && $row['userid']==$reg ) {
        $pinid = $row['id'] ;
        $check_hw = $row['hw'] ;
        if ($check_hw <=4 ) {
            $res=mysql_query("UPDATE pin SET userid='$reg',status='1',hw=hw+1 WHERE pin='$pin'");

            $_SESSION['user'] = $row['userid'];
            header("Location: access.php");
        } else {
            $errMSG = "Card Limit Exceeded";
        }
    } else {
        $errMSG = "Card Used By Another user Or Limit Exceeded";
    }
}

这就是我想做的请帮忙
if（用户输入pin）{从pins中选择status，其中pin=pin if（status=“used”或pin绑定到输入的学生id以外的其他id）{echo“card used and buy new scratch card”标题（'location:buypin.php'）；}else{header（'location:rightplace.php'）；
将此pin的状态设置为“used”，并将该pin绑定到学生id}
}我确实重写了代码
如果（$错误）{

$res=mysql_query("SELECT id,userid,hw FROM pin WHERE userid=" . (int)$reg);
        $row=mysql_fetch_array($res);
        $count = mysql_num_rows($res); // if regno correct it returns must be 1 row

         if ($row = mysql_fetch_array($res)) {
            $pinid = $row['id'] ;
            $check_hw = $row['hw'] ;
            if ($check_hw <=4 ) {
            $res=mysql_query("UPDATE pin SET userid='$reg',status='1',hw=hw+1 WHERE pin='$pin'");

               $_SESSION['user'] = $row['userid'];
            header("Location: access.php");

            }

                 else {
            $errMSG = "Card Limit Exceeded";
        }
        } else {
            $errMSG = "Card Used By Another user ";
        }

    }

我的工作代码
如果（isset（$\u post['btn-signup']））{

$reg = trim($_POST['reg']);
    $reg = strip_tags($reg);
    $reg = htmlspecialchars($reg);

    $pin = trim($_POST['pin']);
    $pin = strip_tags($pin);
    $pin = htmlspecialchars($pin);

$res=mysqli_query($con,"SELECT * FROM pin WHERE pin ='$pin'");
$row=mysqli_fetch_array($res);
$check_id = $row['userid'];
    // checking if the colum userid is empty 
    if ('' !== $row['userid']){    
       // if userid colum is not empty,reg no is correct and limit more than 4
       if ($row['userid']==$reg && $row['hw']<=4) {
            $errMSG = "log";

            }else {
            $errMSG = " Card Used Or  Limit Exceeded";
    }
    }else{

$errMSG = "log";

          }

}
？>非常感谢