php – SimpleXML基于属性值获取元素内容

参见英文答案 > Implementing condition in XPath 2
我正在尝试根据属性的值访问元素的内容.使用PHP SimpleXML.我有以下XML设置：

<DocSum> 
    <Id>21242919</Id> 
    <Item Name="Author" Type="String">Nguyen T</Item>
    <Item Name="Title" Type="String">[Hemoptysis and spontaneous rupture of a primary renal angiosarcoma: a case report.]</Item>
</DocSum>
<DocSum> 
    <Id>21242919</Id> 
    <Item Name="Author" Type="String">Oliveira GC</Item>
    <Item Name="Title" Type="String">disclosing ambiguous gene aliases by automatic literature profiling.</Item>
</DocSum>
<DocSum> 
    <Id>21242919</Id> 
    <Item Name="Author" Type="String">Vanderwall DE</Item>
    <Item Name="Title" Type="String">Metformin and digestive disorders.</Item>
</DocSum>

这些都是书.在这种情况下,我试图获得标题.我到目前为止是这样的：

$xml = simplexml_load_file(url);
$docs = $xml->DocSum;
foreach($docs as $book){
        // Each book individual
}

哪里的评论是我尝试了很多东西.

SimpleXML对象上的此 XPath查询将返回所有具有“Author”属性的Item子项的所有DocSum节点,并在文本节点中返回值“Olivera GC”

$nodes = $xml->xpath('//DocSum[Item[@Name="Author" and .="Oliveira GC"]]');
$book = $nodes[0];
print_r($book);