0

I'm working on a project at home to teach myself PHP PDO. My project is to create a basic version of twitter from scratch. But I'm stuck. What I want to do is to show a list of users (ordered by id) which I can do fine but beside that list of users I want to show whether the currently logged in user is following or not following that person so I can display a link to follow or unfollow them. From what I can see, this really is a question about arrays and foreach loops.

The relevant two tables in the database looks like this (with example data):

users:
id | username
1 | Josh
2 | Sam
3 | Jane

following:
user_id | follower_id
2 | 1
3 | 1

So for example, the currently logged in user Josh (with an id of 1) is following Sam (with an id of 2). A following database row would then say follower_id 1, user_id 2.

I've written two functions to show the id and username of all my users and another to show who the currently logged in person is following. Here they are:

    function show_users(){
        $sql = "select id, username from users order by id";
        $stmt = $GLOBALS['db']->prepare($sql);
        $stmt->execute();
        $result = $stmt->fetchAll(PDO::FETCH_ASSOC);        
        return $result;
    }

    function check_follow($userid){
        $sql= "SELECT DISTINCT user_id FROM following WHERE follower_id = '$userid' ";
        $stmt = $GLOBALS['db']->prepare($sql);
        $stmt->execute();
        $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
        return $result;
    }

This all works fine if I just want to show a list of users ordered by id.

But what I want to do is to show beside the list of users a column that shows whether you are f ollowing that person i.e. and provide a link to 'follow' or 'unfollow' them.

At the moment, the relevant part of my page looks like this:

<?php

$userid = $_SESSION['user']['id'];
$following = check_follow($userid);
$rows = show_users();

?> 

<h1>Follow list</h1> 
<table> 
    <tr> 
        <th>id</th> 
        <th>Username</th>
        <th>Follow status</th> 
    </tr> 
<?php foreach($rows as $row): ?> 
    <tr> 
        <td><?php echo $row['id']; ?></td> 
        <td><?php echo $row['username']; ?></td>
        <td><?php 
            if (in_array($following, $rows)){
                echo "<a href='#'>unfollow</a>";
            }else{
                echo "<a href='#'>follow</a>"; } ?>
    </td> 
    </tr> 
    <?php endforeach; ?> 
</table>

Everything works fine (except for the show who I am/am not follow part), it's not showing 'follow' links for some people and 'unfollow' links for others!

I've spent hours on this. I've read up on arrays, foreach, in_array, PDO fetch statements and tutorials on outputting different data and none of it helps. It doesn't either help that most of the stuff out there is non-pdo.

SOS :)

4

2 回答 2

1

您不想遍历一个结果集，然后对每一行进行查询。它效率低下，数据库可以为您完成。

尝试连接查询：

SELECT u.id, u.username, IF(f.follower_id IS NULL, 0, 1) as following
FROM users u
LEFT JOIN following f
  ON u.id = f.user_id
  AND f.follower_id = $loggedinuser

LEFT JOIN 为您提供 users 表中的每一行，然后是后面匹配“ON”子句中的条件的任何行。如果没有匹配项，则这些列在结果中设置为 NULL。

于 2013-06-05T13:00:16.440 回答
0

您现在对一个结果执行两个不同的查询。

你应该离开加入你的“关注”表是这样的

        SELECT 
        `Users`.`userid` as `Users.id`,
        `Followers`.`id` as `Followers.id`
    FROM 
        `users` AS `Users"` 
    LEFT JOIN 
        `followers` AS `Followers` ON (`Users`.`id` = `Followers`.`userid`)

然后，您可以在同一数据集中获取特定用户的关注者，属于一个用户 ID，然后您可以检查您的用户 ID 是否出现在数组中，或者您甚至可以进一步在现有查询中添加子字符串，但你必须先阅读它，在你这样做之前你应该理解它。

于 2013-06-05T13:05:43.687 回答