php - 将多个选项标记为已选择，数据库结果

Question

我有两个表，post_languages(列:languageID、languageName)和post_to_languages( languageID、postID)和一个选择表单。

我想使用数据库中的结果将一个或多个选项标记标记为由 languageID 选择的。不想只显示语言，我想将它们标记为从表 post_languages 提供的语言列表中选择的。

我已经尝试过，但只选择了一种语言，$res仅返回一个ID:

$stmt = $db->prepare('SELECT languageID FROM post_to_languages WHERE postID = :postID');
$stmt->execute(array(':postID'=>$postID));
$result = $stmt->fetch(PDO::FETCH_ASSOC);
$stmt2 = $db->prepare('SELECT languageID, languageName FROM post_languages ORDER BY languageName');
$stmt2->execute();
echo '<select class="post-language form-control" name="postLangID[]" multiple="multiple" required>';
while($row2 = $stmt2->fetch()){
    foreach ($result as $res) {
        if ($row2['languageID'] == $res) {
            $selected = 'selected';
        } else {
            $selected = '';
        }                      
    } 
    echo '<option value="'.$row2['languageID'].'" '.$selected.'>'.$row2['languageName'].'</option>';
}
echo '</select>';

Answer 1

第一个原因是 $stmt 查询。您可以按 postID 字段进行过滤。 第二个是 $res 变量的类型，我认为它是一个 array。请尝试var_dump它。 我认为它可能看起来像:

foreach ($result as $res) {
        if ($row2['languageID'] == $res['languageID']) {
            $selected = 'selected';
        } else {
        $selected = '';
    }                      
} 

如果$postID是一个Array，您也可以尝试以下代码:

$place_holders = implode(',', array_fill(0, count($postID), '?'));
$stmt = $db->prepare("SELECT languageID, languageName, IF(post_languages.languageID IN (SELECT post_to_languages.languageID FROM post_to_languages WHERE post_to_languages.postID IN ($place_holders)), 1, 0) as selected FROM post_languages ORDER BY languageName");
$stmt->execute($postID);
echo '<select class="post-language form-control" name="postLangID[]" multiple="multiple" required>';
while ($row = $stmt->fetch()) {
    if ($row["selected"]) {
      echo '<option value="'.$row['languageID'].'" selected>'.$row['languageName'].'</option>';
    } else {
      echo '<option value="'.$row['languageID'].'">'.$row['languageName'].'</option>';
    }
}
echo '</select>';