XML Feeds & PHP - 限制项目数

Question

我正在浏览BBC新闻XML提要。但是我想做的是将它限制为8或10个提要条目。

我怎样才能做到这一点?

我的代码是:

<?php
  $doc = new DOMDocument();
  $doc->load('http://feeds.bbci.co.uk/news/rss.xml');
  $arrFeeds = array();
  foreach ($doc->getElementsByTagName('item') as $node) {
    $itemRSS = array ( 
      'title' => $node->getElementsByTagName('title')->item(0)->nodeValue,
      'desc' => $node->getElementsByTagName('description')->item(0)->nodeValue,
      'link' => $node->getElementsByTagName('link')->item(0)->nodeValue,
      'date' => $node->getElementsByTagName('pubDate')->item(0)->nodeValue
      );
?>
<h2><a href="<?php echo $itemRSS['link'] ;?>"><?php echo $itemRSS['title']; ?></a></h2>
<?php  } ?>

Thanks in advance.

Answer 1

使用XPath可以很容易地检索RSS提要的子集。

$itemCount = 10;
$xml = simplexml_load_file('http://feeds.bbci.co.uk/news/rss.xml');
$items = $xml->xpath(sprintf('/rss/channel/item[position() <= %d]', $itemCount));
foreach ($items as $i) {
    $itemRSS = array ( 
        'title' => (string)$i->title,
        'desc' => (string)$i->description,
        'link' => (string)$i->link,
        'date' => (string)$i->pubDate
    );
}

通过用SimpleXML对象交换DOM对象，您的重量会轻一些—并且XPath更容易与SimpleXML一起使用(这就是我在本例中使用它的原因)。对DOM也可以这样做:

$doc = new DOMDocument();
$doc->load('http://feeds.bbci.co.uk/news/rss.xml');
$xpath = new DOMXpath($doc);
$items = $xpath->query(sprintf('/rss/channel/item[position() <= %d]', $itemCount));
foreach ($items as $i) {
    // ...
}

Answer 2

取一个计数器变量，每次迭代递增1，检查计数器是否达到上限，然后退出循环。

$cnt=0;
foreach ($doc->getElementsByTagName('item') as $node) {
    if($cnt == 8 ) {
       break;
     }    
    $itemRSS = array ( 
      'title' => $node->getElementsByTagName('title')->item(0)->nodeValue,
      'desc' => $node->getElementsByTagName('description')->item(0)->nodeValue,
      'link' => $node->getElementsByTagName('link')->item(0)->nodeValue,
      'date' => $node->getElementsByTagName('pubDate')->item(0)->nodeValue
      );
      $cnt++;
?>    
<h2><a href="<?php echo $itemRSS['link'] ;?>"><?php echo $itemRSS['title']; ?></a></h2>
<?php 
} ?>

Answer 3

当您使用SimpleXml时，您也可以使用array_slice:

$rss = simplexml_load_file('http://feeds.bbci.co.uk/news/rss.xml');
$items = $rss->xpath('/rss/channel/item');
$startAtItem = 0;
$numberOfItems = 9;
$firstTenItems = array_slice($items, $startAtItem, $numberOfItems);

或带LimitIterator:

$rss = simplexml_load_file('http://feeds.bbci.co.uk/news/rss.xml');
$items = $rss->xpath('/rss/channel/item');
$startAtItem = 0;
$numberOfItems = 9;
$firstTenItems = new LimitIterator(
    new ArrayIterator($items), $startAtItem, $numberOfItems
);
foreach ($firstTenItems as $item) { …

更优雅的是本站点其他地方提供的XPath position()解决方案。