php - 如何编写投票系统？

Question

我刚开始自学 php。我正在给自己做微型项目来插入自己。

到目前为止，我有一个 MYSQL 数据库，它是通过 php 表单创建的。一栏是业力。我将数据库表的值显示在一个 html 表中，在每一行的末尾，我想点击一个超链接，比如说一个加号，将该行的业力水平增加 1。然后是加号会消失。

我应该让每一行都有一个自动递增的整数作为主键。

Answer 1

对于此示例，我们假设您要对这样的答案进行投票。这至少需要三个表:

用户、答案、投票

投票表将保存所有历史记录:

voteid | userid | answerid | value
----------------------------------
   1   |   12   |   383    |   1
   2   |   28   |   383    |  -1  (negative number would require signed values)

在这个例子中，我们看到记录了两张选票。用户 12 和 28 都对答案 383 进行了投票。用户 12 喜欢它，并为其支持添加了 1。用户 28 不喜欢它，并从其支持中减去 1。

每当用户投票时，您都应该首先检查该用户是否已经对该特定问题进行了投票。如果他们有，您可以拒绝任何进一步的投票尝试，或用新的投票覆盖他们的旧投票。

SELECT * 
FROM votes 
WHERE (userid = 12) 
  AND (answerid = 383)

这是一个非常简单的示例查询，它会告诉您用户是否已经投票。如果它返回记录，你就知道他们已经投票了。您可以非常友善地回应“抱歉，您已经投票了”。消息，或者您可以覆盖它:

UPDATE votes 
SET value = $votevalue 
WHERE (userid = 12) 
  AND (answerid = 383)

话虽如此，让我们看看 SO 是如何实现这一点的:

当您单击赞成票箭头时，SO 会向如下网址发出请求:

    http://stackoverflow.com/posts/1303528/vote/2

In this URL, we can see the vote is being cast on post #1303528. And the vote-type is represented by 2. This 2 likely represents "add one." You could use a more basic url, and go with something like:

    vote.php?answerid=383&vote=1

The vote.php page would have code similar to the following:

(warning: do not use this code as-is. It is meant to be an example, not a solution)

if ($_GET) {

  $userid   = $_SESSION["userid"]; // assumes the user is logged in via SESSIONS
  $answerid = $_GET["answerid"];
  $votetype = $_GET["vote"];

  $query = "SELECT * 
            FROM votes 
            WHERE (userid = {$userid}) 
              AND (answerid = {$answerid})";

  $result = mysql_query($query) or die(mysql_error());

  if (mysql_num_rows($result) > 0) {
    # User has voted
    print "Sorry, you are only allowed one vote.";
  } else {
    # User has not voted, cast the vote
    $query = "INSERT INTO votes (userid, answerid, votevalue)
              VALUES({$userid},{$answerid},{$vote})";
    $result = mysql_query($query) or die(mysql_error());
    if (mysql_affected_rows($result) > 0) {
      print "Your vote has been recorded.";
    }
  }

}