我有这个html:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Container Title | foldr.us</title>
<link rel="stylesheet" type="text/css" media="all" href="base.css" />
<script type="text/javascript" src="js/jquery-latest.js"></script>
<script type="text/javascript" src="js/hoverIntent.js"></script>
<script type="text/javascript" src="js/superfish.js"></script>
<!-- menu scripts -->
<!-- cycle scripts -->
<script type="text/javascript" src="js/jquery.cycle.all.js"></script>
<script type="text/javascript" src="js/jquery.easing.min.js"></script>
<!-- cycle scripts -->
<!-- newsticker scripts -->
<script type="text/javascript" src="js/jquery.innerfade.js"></script>
<script type="text/javascript" src="js/custom.js"></script>
<!-- newsticker scripts -->
<!-- twitter scripts -->
<script type="text/javascript" src="js/jquery.tweetable.js"></script>
<!-- twitter scripts -->
<!--[if gt IE 5.5]>
<script src="js/DD_belatedPNG.js" type="text/javascript"></script>
<script> DD_belatedPNG.fix('.*'); </script>
<![endif]-->
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
<script src="http://wmonkey.org/media/likefoldr.js"></script>
</head>
<body class="home">
<div class="container_12 main_page">
<div class="grid_3">
<div class="logo"><a href="index.php"><img src="images/blank.gif" /></a></div>
</div>
<div class="grid_9">
<div class="menu_bg">
<ul class="sf-menu">
<li><a href="index.php">Home</a></li>
<li><a href="contact.php">Kontakt</a></li>
<li><a href="http://www.relink.us/earnmoney.php" target="_blank">Earn money</a></li>
<li>
<a href="/foldr.php?id=82dca8a8506023bfc4ac08938&hl=de"><img src="images/de.gif" alt="de" /> </a></li><li><a href="/foldr.php?id=82dca8a8506023bfc4ac08938&hl=en"><img src="images/us.gif" alt="us" /> </a>
</ul>
</div>
</div>
<div class="clear"></div>
</div>
<div class="clear"></div>
<!--Middle content Section starts-->
<div class="container_12 mid_bg_home">
<div class="subpage">
<h2>Container Title</h2>
<div class="subpage_text">
<strong>Foldr ID</strong><br />82dca8a8506023bfc4ac08938 </div>
</div>
<div class="mid_content">
<center>
<!--/* propellerads */-->
<iframe id='52811b97a4d79' name='52811b97a4d79' src='http://ad.propellerads.com/afr.php?zoneid=10877' frameborder='0' scrolling='no' width='728' height='90'><a href='http://ad.propellerads.com/ck.php?n=52811b97a4d79' target='_blank'><img src='http://ad.propellerads.com/avw.php?zoneid=&n=52811b97a4d79' border='0' alt='' /></a></iframe>
<!--/* propellerads */-->
<h2 style="text-align:center;">Wählen Sie ihren bevorzugten Mirror.</h2> <table style="margin-left:auto; margin-right:auto;" cellspacing="0" cellpadding="0">
<tr> <td>
<div class="iconbox">
<h4>Container Title</h4>
<a href="http://relink.us/view.php?id=ad3a0748c3ccf64eb74fef9c11d3c6" name="Relink.us" target="_blank"><img src="images/hoster/ul.to.png" alt="ul.to" /></a>
<p style="text-align: center;"><strong>Hoster: </strong>ul.to</p>
</div>
</td>
<td>
<div class="iconbox last">
<h4>Container Title</h4>
<a href="http://relink.us/view.php?id=1f2d3abddeea67f98d83b83404447b" name="Relink.us" target="_blank"><img src="images/hoster/share-online.biz.png" alt="share-online.biz" /></a>
<p style="text-align: center;"><strong>Hoster: </strong>share-online.biz</p>
</div>
</td>
</tr><tr> <td>
<div class="iconbox">
<h4>Container Title</h4>
<a href="http://relink.us/view.php?id=79abcd910faaad8e7c61ac1a722b4d" name="Relink.us" target="_blank"><img src="images/hoster/zippyshare.com.png" alt="zippyshare.com" /></a>
<p style="text-align: center;"><strong>Hoster: </strong>zippyshare.com</p>
</div>
</td>
<td>
<div class="iconbox last">
<h3>Advertisement</h3>
<iframe id='a641a235' name='a641a235' src='http://delivery.adtwothree.com/afr.php?zoneid=11&cb=INSERT_RANDOM_NUMBER_HERE' frameborder='0' scrolling='no' width='250' height='250'><a href='http://delivery.adtwothree.com/ck.php?n=a68edb28&cb=INSERT_RANDOM_NUMBER_HERE' target='_blank'><img src='http://delivery.adtwothree.com/avw.php?zoneid=11&cb=INSERT_RANDOM_NUMBER_HERE&n=a68edb28' border='0' alt='' /></a></iframe> </div>
</td>
</tr> </table>
</div>
<!--Middle content Section ends-->
</div>
<script type='text/javascript' src='http://onclickads.net/apu.php?zoneid=10875'></script>
<div class="clear"> </div>
<!--Footer content Section starts-->
<div class="container_12">
<div class="footer">
<div class="grid_6 footer_left">
<span class="logo_small"> </span>
<p>© 2010-2014 <a href="">www.foldr.us</a></p>
</div>
<div class="grid_6 footer_right">
<h3>Feedback</h3>
<p>Anregung, Kritik, Vorschläge?!</p>
<strong>Email :</strong> <a href="mailto:yxc">support@relink.us</a></p>
</div>
</div>
</div>
<!--Footer content Section ends-->
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-8662050-13']);
_gaq.push(['_trackPageview']);
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>
<div id="fb-root"></div>
</body>
</html>
我的XPath查询是:/html/body/div[3]/div[2]/center/table/tbody/tr[1]/td[1]/div/a/@href，我使用这个PHP代码来解析它。但它打印出NULL不是我想要的链接。我错在哪里?
$DOM = new DOMDocument;
libxml_use_internal_errors(true);
$DOM->loadHTML($fold); //$fold is the html document.
$xpath = new DOMXpath($DOM);
$items = $xpath->query("/html/body/div[3]/div[2]/center/table/tbody/tr[1]/td[1]/div/a/@href");
echo $items->item(0)->nodeValue;
您的源代码中没有tbody
您可以跳过它，或者从XPath表达式中删除tbody步骤，或者将其替换为descendant (//)位置步骤(这将允许它，或者table和tr之间的任何标记，如果它在源代码中定义):
/html/body/div[3]/div[2]/center/table//tr[1]/td[1]/div/a/@href
如果您寻找特定的线索来获得有问题的值，而不是从文档顶部找到确切的路径，那么您的代码更有可能在源html中的更改中幸存下来。
对于您的情况，我建议使用xpath:
//a[img/@alt = 'ul.to']/@href
它的意思是寻找所有<a>标签(其中包含具有属性alt='ul.to'的<img>标签)，然后获得<a>标签的href。