在多维数组中回显特定元素 ID 的值

Question

我正在编写一个脚本来输出从 PubMed Central API 抓取的排序信息。我的问题是我想提取第一作者和第二作者以及第一个和第二个关键字（就这个问题而言，我们可以只关注一个）。 $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'contrib-group'}->contrib->name->surname 就是一个很好的例子。很明显，我可以打印第一个名字。

通过阅读其他帖子，我了解到我需要一个 foreach 循环来实现我想要的。但是，我不明白如何在这种情况下实现这一点。我的代码如下：

<?php
$PMCID = 3545513;
$url = 'http://www.pubmedcentral.nih.gov/oai/oai.cgi?verb=GetRecord&identifier=oai:pubmedcentral.nih.gov:'.$PMCID.'&metadataPrefix=pmc_fm';
$xml = new SimpleXMLElement(file_get_contents($url));
?>
<table>
<tr>
<td>Journal Title</td><td>Year</td><td>Issue</td><td>NOC_Country</td><td>State</td><td>City</td><td>Primary Institution</td><td>Secondary Institution</td><td>First Author</td><td>Second Author</td><td>Topic</td><td>Target Behavior 1</td><td>Target Behavior 2</td><td>Population</td><td>Paper</td><td>Status</td>
</tr>
<tr>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'journal-meta'}->{'journal-title-group'}->{'journal-title'};?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'pub-date'}->year;?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->issue;?></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'contrib-group'}->contrib->name->surname;?>, <?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'contrib-group'}->contrib->name->{'given-names'};?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'contrib-group'}->contrib->name->surname;?>, <?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'contrib-group'}->contrib->name->{'given-names'};?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'title-group'}->{'article-title'};?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'kwd-group'}->kwd;?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'kwd-group'}->kwd;?></td>
<td></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'article-categories'}->{'subj-group'}->subject;?></td>
<td></td>
</tr>
</table>

任何帮助将不胜感激！

Answer 1

结束于：

<table>
<tr>
<td><strong>Journal Title</strong></td><td><strong>Year</strong></td><td><strong>Issue</strong></td><td><strong>First Author</strong></td><td><strong>Second Author</strong></td><td><strong>Topic</strong></td><td><strong>Target Behavior 1</strong></td><td><strong>Target Behavior 2</strong></td><td><strong>Paper</strong></td>
</tr>
<?php
$PMCID = $_REQUEST['PMCID'];
$url = 'http://www.pubmedcentral.nih.gov/oai/oai.cgi?verb=GetRecord&identifier=oai:pubmedcentral.nih.gov:'.$PMCID.'&metadataPrefix=pmc_fm';
$xml = new SimpleXMLElement(file_get_contents($url));
?>
<tr>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'journal-meta'}->{'journal-title-group'}->{'journal-title'};?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'pub-date'}->year;?></td>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->issue;?></td>
<?php
$n=0;
foreach($xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'contrib-group'} as $author){
    echo "<td>" . $author->contrib->name->surname . ", ";
    echo $author->contrib->name->{'given-names'} . "</td>";
$n++;
if($n==2) break;
}
unset($n);
unset($author);
?>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'title-group'}->{'article-title'};?></td>
<?php
$i=0;
foreach($xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'kwd-group'}->kwd as $keyword){
    echo "<td>" . $keyword . "</td>";
$i++;
if($i==2) break;
}
unset($i);
unset($keyword);
?>
<td><?php echo $xml->GetRecord->record->metadata->article->front->{'article-meta'}->{'article-categories'}->{'subj-group'}->subject;?></td>
</tr>
</table>