Question

我很难从数组中获取正确的数据。我编写了一个嵌套的foreach循环，但内部循环抛出了“为foreach（）提供的无效参数”错误。有人可以帮我解决这个问题吗？感谢。

foreach($row as $val)
{
    echo $val['title'].'<br>';
    echo $val['author'].'<br>';
    echo $val['post'].'<br>';
    echo $val['entry_date'].'<br>';
    echo $val['comments'].'<br>';

    foreach($val as $val2)
    {
        echo $val['comments'].'<br>';
    }
}

Array
(
    [title] => First Blog
    [author] => Administrator
    [post] => Testing entry number one
    [entry_date] => Fri, 23 Oct 2009
    [comments] => Array
        (
            [0] => Array
                (
                    [commenter] => Sally Anderson
                    [comments] => comment 1 post 1
                    [comment_date] => October 24th, 2009 at 5:24 AM
                )

            [1] => Array
                (
                    [commenter] => Mike Jones
                    [comments] => comment 2 post 1
                    [comment_date] => October 24th, 2009 at 5:21 AM
                )
        )
)
Array
(
    [title] => Second Blog
    [author] => Administrator
    [post] => Testing entry number two
    [entry_date] => Sat, 24 Oct 2009
    [comments] => Array
        (
            [0] => Array
                (
                    [commenter] => Sally Anderson
                    [comments] => comment 1 post 2
                    [comment_date] => October 24th, 2009 at 5:21 AM
                )

            [1] => Array
                (
                    [commenter] => Mike Jones
                    [comments] => comment 2 post 2
                    [comment_date] => October 24th, 2009 at 5:21 AM
                )
        )
)

Answer 1

假设$rows是问题底部的结构（数组数组），那么：

foreach ($rows as $row) {
  echo <<<END
$row[title]<br>
$row[author]<br>
$row[post]<br>
$row[entry_date]<br>
END;
  foreach ($row['comments'] as $comment) {
    echo <<<END
$comment[comments]<br>
$comment[commentor]<br>
$comment[comment_date]<br>
END;
  }
}

我强烈建议您选择有意义的名称（例如$comment和$row），而不是像$val和$val2那样无意义的名称，因为这些名称只会引起混淆。< / p>

此外，我在修订版中使用了heredoc syntax因为我倾向于认为可以使事情更具可读性，但这是可选的。一个更好的选择可能是：

<?php foreach ($rows as $row): ?>
<?php echo $row['title'] ?><br>
<?php echo $row['post'] ?><br>
<?php echo $row['entry_date'] ?><br>
<?php foreach ($row['comments'] as $comment): ?>
<?php echo $comment['comments'] ?><br>
<?php echo $comment['commentor'] ?><br>
<?php echo $comment['comment_date'] ?><br>
<?php endforeach; ?>
<?php endforeach; ?>

如果您散布了大量HTML，这可能很有用。以上内容切换为使用alternative control structures，这是可选的，但在此类代码中通常被认为更具可读性。

最后，你可以PHP short tags，有些人不喜欢（因为它们可能被禁用或与XML处理指令接口）但我通常更喜欢：

<? foreach ($rows as $row): ?>
<?= $row['title'] ?><br>
<?= $row['post'] ?><br>
<?= $row['entry_date'] ?><br>
<? foreach ($row['comments'] as $comment): ?>
<?= $comment['comments'] ?><br>
<?= $comment['commentor'] ?><br>
<?= $comment['comment_date'] ?><br>
<? endforeach; ?>
<? endforeach; ?>

Answer 2

变化

foreach($val as $val2)
{
    echo $val['comments'].'<br>';
}

到

foreach($val['comments'] as $val2)
{
    echo $val2['comments'].'<br>';
}

如何编写一个能产生我想要的结果的foreach

2 个答案: