如何用PHP xpath函数结合SimpleXML解析XML？详细使用示例分享

二、XPath简介

XPath是一种用来在XML文档中定位节点的语言，SimpleXML自带xpath()方法，可以利用XPath表达式查询节点。

三、结合SimpleXML与XPath解析XML的示例

假设我们需要从如下XML中获取所有book节点中，author是“李四”的书籍标题。

<span><span><span class="hljs-variable">$xmlString</span></span><span> = <span class="hljs-string">&lt;&lt;&lt;XML
&lt;books&gt;
    &lt;book id="1"&gt;
        &lt;title&gt;PHP入门&lt;/title&gt;
        &lt;author&gt;张三&lt;/author&gt;
    &lt;/book&gt;
    &lt;book id="2"&gt;
        &lt;title&gt;XML</span>解析实战&lt;/title&gt;
        &lt;author&gt;李四&lt;/author&gt;
    &lt;/book&gt;
    &lt;book id=</span><span><span class="hljs-string">"3"</span></span><span>&gt;
        &lt;title&gt;深入理解PHP&lt;/title&gt;
        &lt;author&gt;李四&lt;/author&gt;
    &lt;/book&gt;
&lt;/books&gt;
XML;

</span><span><span class="hljs-variable">$xml</span></span><span> = </span><span><span class="hljs-title function_ invoke__">simplexml_load_string</span></span><span>(</span><span><span class="hljs-variable">$xmlString</span></span><span>);

</span><span><span class="hljs-comment">// XPath查询author为李四的book节点</span></span><span>
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$xml</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">xpath</span></span><span>(</span><span><span class="hljs-string">"//book[author='李四']"</span></span><span>);

</span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$result</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$book</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"书名："</span></span><span> . </span><span><span class="hljs-variable">$book</span></span><span>-&gt;title . </span><span><span class="hljs-string">"\n"</span></span><span>;
}
</span></span>

运行结果：

<span><span>书名：</span><span><span class="hljs-type">XML</span></span><span>解析实战
书名：深入理解PHP
</span></span>

四、XPath表达式说明

• //book：选取所有book节点

• [author='李四']：过滤条件，选出author节点值为“李四”的book节点

五、更多实用示例

1. 获取某个节点属性

获取所有book的id属性：

<span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$xml</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">xpath</span></span><span>(</span><span><span class="hljs-string">"//book"</span></span><span>) </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$book</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"书ID："</span></span><span> . </span><span><span class="hljs-variable">$book</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>] . </span><span><span class="hljs-string">"\n"</span></span><span>;
}
</span></span>

2. 复杂查询

获取id大于1的书：

<span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$xml</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">xpath</span></span><span>(</span><span><span class="hljs-string">"//book[@id &gt; 1]"</span></span><span>);
</span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$result</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$book</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$book</span></span><span>-&gt;title . </span><span><span class="hljs-string">"\n"</span></span><span>;
}
</span></span>

六、总结

• 使用simplexml_load_string()或simplexml_load_file()加载XML。

• 利用xpath()方法配合XPath表达式灵活定位节点。

• 可以通过属性数组方式访问节点属性。

• XPath表达式功能强大，可支持多种筛选和路径定位。

掌握了SimpleXML和XPath的结合使用，能够让PHP开发者高效处理各种XML数据，提升程序的灵活性和可维护性。