使用 PHP 进行 XPath 查询
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XPath query with PHP
提问by liewl
Here's the XML code I'm working with:
这是我正在使用的 XML 代码：
<inventory>
<drink>
<lemonade supplier="mother" id="1">
<price>.50</price>
<amount>20</amount>
</lemonade>
<lemonade supplier="mike" id="4">
<price>.00</price>
<amount>20</amount>
</lemonade>
<pop supplier="store" id="2">
<price>.50</price>
<amount>10</amount>
</pop>
</drink>
</inventory>
Then I wrote a simple code to practice working with XPath:
然后我写了一个简单的代码来练习使用 XPath：
<?php
$xmldoc = new DOMDocument();
$xmldoc->load('sample.xml');
$xpathvar = new Domxpath($xmldoc);
$queryResult = $xpathvar->query('//lemonade/price');
foreach($queryResult as $result) {
echo $result->textContent;
}
?>
That code is working well, outputting all the lemonade price values as expected. Now when i change the query string to select only the elements with an attribute set to a certain value, like
该代码运行良好，按预期输出所有柠檬水价格值。现在，当我更改查询字符串以仅选择属性设置为特定值的元素时，例如
//lemonade[supplier="mother"]/price
//柠檬水[supplier="mother"]/价格
or
或者
//lemonade[id="1"]/price
//柠檬水[id="1"]/价格
it won't work, no output at all. What am i doing wrong?
它不会工作，根本没有输出。我究竟做错了什么？
回答by bobwienholt
Try this:
尝试这个：
//lemonade[@id="1"]/price
or
或者
//lemonade[@supplier="mother"]/price
Without the "@" it looks for child elements with that name instead of attributes.
如果没有“@”，它会查找具有该名称而不是属性的子元素。
回答by Tirno
This is only tangentially related, but when you use XPath on a document for which you know the structure, don'tuse "//some-element-name". It's very nice for a quick example, but when you hit a huge xml file with that query, particularly if it is followed by something complex, you will quickly run into performance issues.
这只是切线相关，但是当您在知道其结构的文档上使用 XPath 时，不要使用“//some-element-name”。作为一个简单的例子，这非常好，但是当您使用该查询访问一个巨大的 xml 文件时，特别是如果它后面跟着一些复杂的东西，您将很快遇到性能问题。
inventory/drink/lemonade[@supplier="mother"]/price
库存/饮料/柠檬水[@supplier="mother"]/价格
回答by Kris
you have to use the @ sign to indicate attribute within the predicate like so: //lemonade[@supplier="mother"]/price, that's all.
您必须使用 @ 符号来指示谓词中的属性，如下所示：//lemonade[@supplier="mother"]/price，仅此而已。
