未定义的命名空间前缀 - Undefined namespace prefix

我正在使用雅虎天气API

$result = file_get_contents('https://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20weather.forecast%20where%20woeid%20in%20(select%20woeid%20from%20geo.places(1)%20where%20text%3D%22Sarajevo%22)&format=xml&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys');
$xml = simplexml_load_string($result);
//echo htmlspecialchars($result, ENT_QUOTES, 'UTF-8');
$xml->registerXPathNamespace('yweather', 'http://xml.weather.yahoo.com/ns/rss/1.0');
    $weather_location = $xml->channel->xpath('yweather:location');
    if(!empty($weather_location)){
        foreach($xml->channel->item as $item){
            
           $forecast = $item->xpath('yweather:forecast');    
           $time =  time();
           $wdate = strtotime($forecast[$i]['day']);
    
           echo "".(string)$wdate."";  // Wed       
           echo "<span><b>".(int)$forecast[$i]['high']."°</b>";// 8
           echo "&nbsp;".(int)$forecast[$i]['low']."°</span>"; // 19      
        }            
}

示例XML:

<?xml version="1.0" encoding="UTF-8"?>
<query xmlns:yahoo="http://www.yahooapis.com/v1/base.rng"
    yahoo:count="1" yahoo:created="2016-03-31T10:56:53Z" yahoo:lang="en-US">
    <results>
        <channel>
            <yweather:units
                xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                distance="mi" pressure="in" speed="mph" temperature="F"/>
            <title>Yahoo! Weather - Sarajevo, Federacija Bosne I Hercegovine, BA</title>
            <link>http://us.rd.yahoo.com/dailynews/rss/weather/Country__Country/*https://weather.yahoo.com/country/state/city-943828/</link>
            <description>Yahoo! Weather for Sarajevo, Federacija Bosne I Hercegovine, BA</description>
            <language>en-us</language>
            <lastBuildDate>Thu, 31 Mar 2016 12:56 PM CEST</lastBuildDate>
            <ttl>60</ttl>
            <yweather:location
                xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                city="Sarajevo" country="Bosnia and Herzegovina" region=" Federacija Bosne I Hercegovine"/>
            <yweather:wind
                xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                chill="70" direction="270" speed="4"/>
            <yweather:atmosphere
                xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                humidity="43" pressure="922.0" rising="0" visibility="16.1"/>
            <yweather:astronomy
                xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                sunrise="6:27 am" sunset="7:14 pm"/>
            <image>
                <title>Yahoo! Weather</title>
                <width>142</width>
                <height>18</height>
                <link>http://weather.yahoo.com</link>
                <url>http://l.yimg.com/a/i/brand/purplelogo//uh/us/news-wea.gif</url>
            </image>
            <item>
                <title>Conditions for Sarajevo, Federacija Bosne I Hercegovine, BA at 12:00 PM CEST</title>
                <geo:lat xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#">43.853161</geo:lat>
                <geo:long xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#">18.38493</geo:long>
                <link>http://us.rd.yahoo.com/dailynews/rss/weather/Country__Country/*https://weather.yahoo.com/country/state/city-943828/</link>
                <pubDate>Thu, 31 Mar 2016 12:00 PM CEST</pubDate>
                <yweather:condition
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="32" date="Thu, 31 Mar 2016 12:00 PM CEST"
                    temp="69" text="Sunny"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="30" date="31 Mar 2016" day="Thu" high="70"
                    low="41" text="Partly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="28" date="01 Apr 2016" day="Fri" high="72"
                    low="50" text="Mostly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="30" date="02 Apr 2016" day="Sat" high="68"
                    low="44" text="Partly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="30" date="03 Apr 2016" day="Sun" high="69"
                    low="45" text="Partly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="30" date="04 Apr 2016" day="Mon" high="69"
                    low="47" text="Partly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="30" date="05 Apr 2016" day="Tue" high="69"
                    low="47" text="Partly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="30" date="06 Apr 2016" day="Wed" high="69"
                    low="47" text="Partly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="28" date="07 Apr 2016" day="Thu" high="66"
                    low="49" text="Mostly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="28" date="08 Apr 2016" day="Fri" high="58"
                    low="50" text="Mostly Cloudy"/>
                <yweather:forecast
                    xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"
                    code="28" date="09 Apr 2016" day="Sat" high="58"
                    low="47" text="Mostly Cloudy"/>
                <description>&lt;![CDATA[&lt;img src="http://l.yimg.com/a/i/us/we/52/32.gif"/&gt;
&lt;BR /&gt;
&lt;b&gt;Current Conditions:&lt;/b&gt;
&lt;BR /&gt;Sunny
&lt;BR /&gt;
&lt;BR /&gt;
&lt;b&gt;Forecast:&lt;/b&gt;
&lt;BR /&gt; Thu - Partly Cloudy. High: 70Low: 41
&lt;BR /&gt; Fri - Mostly Cloudy. High: 72Low: 50
&lt;BR /&gt; Sat - Partly Cloudy. High: 68Low: 44
&lt;BR /&gt; Sun - Partly Cloudy. High: 69Low: 45
&lt;BR /&gt; Mon - Partly Cloudy. High: 69Low: 47
&lt;BR /&gt;
&lt;BR /&gt;
&lt;a href="http://us.rd.yahoo.com/dailynews/rss/weather/Country__Country/*https://weather.yahoo.com/country/state/city-943828/"&gt;Full Forecast at Yahoo! Weather&lt;/a&gt;
&lt;BR /&gt;
&lt;BR /&gt;
(provided by &lt;a href="http://www.weather.com" &gt;The Weather Channel&lt;/a&gt;)
&lt;BR /&gt;
]]&gt;</description>
                <guid isPermaLink="false"/>
            </item>
        </channel>
    </results>
</query>

这就是结果：

警告：SimpleXMLElement:：xpath（）[SimpleXMLElement.xpath]：第8行/home/ugbosnia/public_html/blocks/weather/block.php中未定义的命名空间前缀
警告：SimpleXMLElement:：xpath（）[simplexxmlelement.xpath]：xmlXPathEval:在第8行的/home/ugbosnia/public_html/blocks/weather/block.php中评估失败

有什么建议吗？

channel不是文档元素的子节点。如果读取XML，则文档元素为query，其中包含一个子results。我建议将channel存储在它自己的变量中：

$channel = $xml->results->channel;

在使用其xpath()方法之前，您必须在每个SimpleXMLElement上注册命名空间。在您的情况下，您在$xml上注册它，但不在$channel或$item对象上注册它。$xml=simplexml_load_string（$result）；

$channel = $xml->results->channel;
$channel->registerXPathNamespace('yweather', 'http://xml.weather.yahoo.com/ns/rss/1.0');
$weather_location = $channel->xpath('yweather:location');
if(!empty($weather_location)){
  foreach($channel->item as $item){
    $item->registerXPathNamespace('yweather', 'http://xml.weather.yahoo.com/ns/rss/1.0');
    $forecast = $item->xpath('yweather:forecast');    
    var_dump($forecast);     
  }      
}

输出：

array(10) {
  [0]=>
  object(SimpleXMLElement)#8 (1) {
    ["@attributes"]=>
    array(6) {
      ["code"]=>
      string(2) "30"
      ["date"]=>
      string(11) "31 Mar 2016"
      ["day"]=>
      string(3) "Thu"
      ["high"]=>
      string(2) "70"
      ["low"]=>
      string(2) "41"
      ["text"]=>
      string(13) "Partly Cloudy"
    }
  }
  [1]=>
  object(SimpleXMLElement)#9 (1) {
   ...

DOM为XPath表达式使用了一个单独的对象，所以您只需要在这个对象上注册名称空间：

$document = new DOMDocument();
$document->loadXml($result);
$xpath = new DOMXpath($document);
$xpath->registerNamespace('yweather', 'http://xml.weather.yahoo.com/ns/rss/1.0');
$weather_location = $xpath->evaluate('//yweather:location');
...

可能是由于最近雅虎天气API的变化，如本文所述：使用OAuth 1 发出雅虎天气API请求