Question

我可以从响应中轻松地从api中提取所需的节点：https://musicbrainz.org/ws/2/release-group/fc02b10c-8a09-38d6-b612-22c47794d2c6?inc=releases+media+url-rels

但是，我试图从下面得到关系类型discogs的目标没有运气，任何帮助赞赏

<relation-list target-type="url">
    <relation type-id="6578f0e9-1ace-4095-9de8-6e517ddb1ceb" type="wikipedia">
        <target id="cba6f347-45b3-4bd5-8b7f-818fa76a63b2">
            http://en.wikipedia.org/wiki/Insineratehymn
        </target>
    </relation>
    <relation type-id="99e550f3-5ab4-3110-b5b9-fe01d970b126" type="discogs">
        <target id="e9e6e840-ca1a-47fa-b835-47d0d86bcda8">
            http://www.discogs.com/master/316106
       </target>
    </relation>
    <relation type-id="b988d08c-5d86-4a57-9557-c83b399e3580" type="wikidata">
        <target id="f9b00d41-6f25-4174-9c72-ba1c452cfa6d">
            http://www.wikidata.org/wiki/Q1932481
        </target>
    </relation>
</relation-list>

Answer 1

检查

    <?php
$url = 'https://musicbrainz.org/ws/2/release-group/fc02b10c-8a09-38d6-b612-22c47794d2c6?inc=releases+media+url-rels';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_HTTPHEADER, Array("User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.15) Gecko/20080623 Firefox/2.0.0.15") ); 
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
$result= curl_exec ($ch);
curl_close ($ch);
$res = simplexml_load_string($result);
//echo "<pre>";
//print_r($res);
$listing = $res->{'release-group'}->{'relation-list'}->relation;

// full listing  
foreach($listing as $list)
{
    echo $list['type']."<br>"; // full listing       
}

//Particular url
foreach($listing as $list)
{
    if($list['type'] == 'discogs') 
    {
        echo $list->target; // Particular url
    }        
}


exit;

<强>输出

wikipedia
discogs
wikidata


http://www.discogs.com/master/316106

Answer 2

您可以使用->attributes()方法检查该特定标记是否包含所需的属性。例如：

// without xpath
$xml = simplexml_load_file('https://musicbrainz.org/ws/2/release-group/fc02b10c-8a09-38d6-b612-22c47794d2c6?inc=releases+media+url-rels');
foreach($xml->{'release-group'}->{'relation-list'}->{'relation'} as $relation) {
    if($relation->attributes()['type'] == 'discogs') { // dereference (5.4 or above)
        echo (string) $relation->target; // http://www.discogs.com/master/316106
    }
}

或者您也可以使用xpath并在xml中注册命名空间，并直接将其作为目标：

$xml->registerXPathNamespace('r', 'http://musicbrainz.org/ns/mmd-2.0#'); // registers xmlns (namespace)
$discogs = (string) $xml->xpath('//r:release-group/r:relation-list/r:relation[@type="discogs"]/r:target')[0];
echo $discogs; // http://www.discogs.com/master/316106

Answer 3

刚刚制作了一个简单的代码：

$xml = simplexml_load_file('https://musicbrainz.org/ws/2/release-group/fc02b10c-8a09-38d6-b612-22c47794d2c6?inc=releases+media+url-rels');
foreach($xml->{'release-group'}->{'relation-list'}->relation as $relation) {
    if($relation['type'] == 'discogs') {
        $link = $relation->target;
    }
}

echo $link;

输出：

http://www.discogs.com/master/316106

Answer 4

XML使用命名空间。 DOM + Xpath允许您考虑到这一点并直接获取字符串值：

$dom = new DOMDocument();
$dom->load(
  'https://musicbrainz.org/ws/2/release-group/fc02b10c-8a09-38d6-b612-22c47794d2c6?inc=releases+media+url-rels'
);
$xpath = new DOMXPath($dom);
$xpath->registerNamespace('mb', "http://musicbrainz.org/ns/mmd-2.0#");

$expression = 'string(
  //mb:release-group
  /mb:relation-list
  /mb:relation[@type = "discogs"]
  /mb:target
)';

var_dump($xpath->evaluate($expression));

输出：

string(36) "http://www.discogs.com/master/316106"

XML PHP，过滤掉特定的“类型”

4 个答案: