XML PHP，过滤掉特定的“类型”

Question

I'm extracting the required nodes from the api easily from the response here : https://musicbrainz.org/ws/2/release-group/fc02b10c-8a09-38d6-b612-22c47794d2c6?inc=releases+media+url-rels

However, i am trying to get the target of relation type discogs from the below with no luck, any help appreciated

<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

Just made a simple code:

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

echo $link;

Output:

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