php - 更新 mySQL 查询无效

Question

我一直在研究学生登录和注册类(class)的一些学生管理系统，登录机制在登录后工作正常，它显示学生姓名、ID 等并要求注册类(class)，当学生选择类(class)时，所选类(class)应更新为数据库，提交页面需要从上一页获取学生ID和类(class)，并相应地更新数据库。

提交后仅将类(class)更新为 $fresh :S

这是 submit.php 代码:

<?php
$dbhost = 'localhost';
$dbuser = 'username';
$dbpass = '123';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
  die('Could not connect: ' . mysql_error());
}

$fresh = $_REQUEST["fresh"]; 
$user_id= $_REQUEST["user_id"]; 


$sql = 'UPDATE courses
    SET fresh="$fresh"
    WHERE user_id=$user_id';

mysql_select_db('registrations');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
  die('Could not update data: ' . mysql_error());
}
echo "Updated data successfully\n";
mysql_close($conn);
?>

Answer 1

试试这个 block 代码。

<?php
    $dbhost = 'localhost';
    $dbuser = 'username';
    $dbpass = '123';
    $database='registrations';
    $conn = mysqli_connect($dbhost, $dbuser, $dbpass,$database);
    if (!$conn || $conn==null) die('Could not connect: ' . mysqli_error($conn));

    $fresh = $_REQUEST["fresh"]; 
    $user_id= $_REQUEST["user_id"]; 


    $sql = "UPDATE courses
        SET fresh='$fresh'
        WHERE user_id=$user_id";

    $retval = mysqli_query($conn, $sql);
    if(! $retval )
    {
      die('Could not update data: ' . mysqli_error($conn));
    }
    else{
    echo "Updated data successfully\n";
    }
    mysqli_close($conn);
    ?>