php对xml的XPath操作

通过DOM结构点位节点，在数据量很大的情况下速度下降的厉害。解决方法是XPath。

XPath作用：用于快速定位节点

XPath实现查询功能：

<?php//XPath$doc = new DOMDocument();$doc->preserveWhiteSpace=false;$doc->load('books.xml');//通过文档生成此文档的路径$xpath = new DOMXPath($doc);//查询所有的书$query = "/books/book/name";$result = $xpath->query($query);foreach ($result as $bookname){    echo $bookname->nodeValue . '<br/>';}echo "<br/>==========================================<br/>";//查询所有静态语言的图书$query = "/books/book[@type='静态语言']/name";$result = $xpath->query($query);foreach ($result as $bookname){    echo $bookname->nodeValue . '<br/>';}echo "<br/>==========================================<br/>";//通过位置来查询$query = "/books/book[position()=3]/name";$result = $xpath->query($query);foreach ($result as $bookname){    echo $bookname->nodeValue . '<br/>';}echo "<br/>==========================================<br/>";

执行结果：