foreach 循环中的 Mysqli_query

Question

我在 foreach 循环中的 mysqli_query 遇到问题，我首先从表中获取字符串，然后将其分成数组。然后我尝试遍历数组并在循环内调用查询。

$langs_result = mysqli_query($con, "SELECT Languages FROM users WHERE Username = '$username'");

    $row = mysqli_fetch_assoc($langs_result);

    $langs = $row['Languages'];
    $userLangs = str_replace(" ","",$langs);
    $userLangs = explode(",",$langs);
    print_r($userLangs);
    $posts = array();

    foreach($userLangs as $lang){
        echo "$lang <br>";
        $sql = "SELECT * FROM posts WHERE Language = '$lang'";
        $getLangPosts = mysqli_query($con, $sql);
        array_push($posts, mysqli_fetch_assoc($getLangPosts));
    }

    print_r($posts);

对于这个用户，语言是德语、意大利语、丹麦语和英语，但是$posts 数组只包含从第一种语言（德语）中找到的第一个帖子，有人可以帮忙吗？我正在尝试获取$userLangs 数组中每种语言的所有帖子。

它正在通过 foreach 循环，因为每次回显的 $lang 变量都会发生变化，但查询仍然无法正常工作。

感谢您的帮助！

Answer 1

select posts.* from posts
left join users on users.language=posts.language
where users.username='your_desiredusername'
group by users.language;

只需尝试通过填写用户名将其作为单个查询运行 无需多次查询

Answer 2

您可以通过执行 JOIN 来避免多个查询，使用 FIND_IN_SET 匹配您的逗号分隔列表。您可能还需要使用 REPLACE 来删除逗号分隔列表中的多余空格。

然后您可以循环显示数据，在更改语言时显示语言：-

<?php

$sql = "SELECT a.Languages AS user_languages, 
                b.*
        FROM users a
        LEFT OUTER JOIN posts b
        ON FIND_IN_SET(b.Language, REPLACE(a.Languages, ' ', ''))
        WHERE a.Username = '$username'
        ORDER BY b.Languages";

$langs_result = mysqli_query($con, $sql);

if($row = mysqli_fetch_assoc($langs_result))
{
    print_r(explode(', ', $row['user_languages']));
    $prev_langauge = '';
    while($row = mysqli_fetch_assoc($langs_result))
    {
        if ($prev_langauge != $row['Languages'])
        {
            if ($prev_langauge != '')
            {
                print_r($posts);
            }
            $posts = array();
            echo $row['Languages']."<br>";
            $prev_langauge = $row['Languages'];
        }
        array_push($posts, mysqli_fetch_assoc($row));
    }
    if ($prev_langauge != '')
    {
        print_r($posts);
    }
}

Answer 3

更新
请参阅此代码：

<?php

$langs_result = mysqli_query($con, "SELECT Languages FROM users WHERE Username = '$username'");

$row = mysqli_fetch_assoc($langs_result);

$langs = $row['Languages'];

// $langs = 'German, Italian, Danish, French'; added this to run the test

// $userLangs = str_replace(" ","",$langs); this is not needed, see the explode below
$userLangs = explode(", ",$langs);

foreach($userLangs as $lang){
    echo $lang;
    $sql = "SELECT * FROM posts WHERE Language = '$lang'";

    $getLangPosts = mysqli_query($con, $sql); // this is the result of the select *
    while($post = mysqli_fetch_assoc($getLangPosts)){ // iterate over all the results
        $postField = $post["yourChoiceField..say..Title"]; // get something from each row
        array_push($posts, $title); // push into array
    }
}

print_r($posts);

由于初始选择基于username，我认为不需要第一个循环，因此您的代码在正确的轨道上。
需要第二个循环来遍历帖子，并需要一个字段来填充 $posts 数组。

---

需要循环执行mysqli_fetch_assoc

$langs_result = mysqli_query($con, "SELECT Languages FROM users WHERE Username = '$username'");

while($row = mysqli_fetch_assoc($langs_result)){

    $langs = $row['Languages'];

    $userLangs = str_replace(" ","",$langs); // i don't get why you are doing this though
    $userLangs = explode(",",$langs);
    print_r($userLangs);

    $posts = array();

    foreach($userLangs as $lang){
        echo "$lang <br>";
        $sql = "SELECT * FROM posts WHERE Language = '$lang'";
        $getLangPosts = mysqli_query($con, $sql);
        array_push($posts, mysqli_fetch_assoc($getLangPosts));
    }

    print_r($posts);
}

了解select 查询实际返回的内容会有所帮助。

Answer 4

mysqli_fetch_assoc 在每次调用时只获取一行，您需要像这样使用它：

while ($row_new = mysqli_fetch_assoc($getLangPosts)){
   array_push($posts, $row_new);
}

Answer 5

需要循环内部查询来获取列数据

foreach($userLangs as $lang){
        echo "$lang <br>";
        $sql = "SELECT * FROM posts WHERE Language = '$lang'";
        $getLangPosts = mysqli_query($con, $sql);

        while($row1 = mysqli_fetch_assoc($getLangPosts))
              array_push($posts, $row1['YOUR_COLUMN_NAME']);
    }

或者你应该使用 IN 子句而不是循环

$langs_result = mysqli_query($con, "SELECT Languages FROM users WHERE Username = '$username'");

while($row = mysqli_fetch_assoc($langs_result)){

$langs = $row['Languages'];
$userLangs = str_replace(" ","",$langs);
$userLangs = explode(",",$langs);
print_r($userLangs);
$posts = array();

$sql = "SELECT * FROM posts WHERE Language IN ('".implode(',',$userLangs)."')";
        $getLangPosts = mysqli_query($con, $sql);

        while($row1 = mysqli_fetch_assoc($getLangPosts))
              array_push($posts, $row1['YOUR_COLUMN_NAME']);
 }