php - 在 xpath 查询中使用 php 变量

Question

我想在 xpath 语句中使用 php 变量。这里有一个类似的线程，其答案不能解决我的问题。

这是示例代码（ $r1 或 $r2 都没有创建预期的数组）

<?php
$xml = simplexml_load_file("menu.xml");
$term = "one";
$r1 = $xml->xpath("//category[@name=$term]");
$r2 = $xml->xpath("//category[@name=" . $term . "]");
$r3 = $xml->xpath("//category[@name='one']");

echo ('$r1 = '); print_r($r1);
echo ('<br>$r2 = '); print_r($r2);
echo ('<br>$r3 = '); print_r($r3);
?>

XML

<?xml version="1.0" encoding="ISO-8859-1"?>
<menu>
<category name="one">
    <item>Tomato and Cheese</item>
    <item>Onions</item>
    <item>Broccoli</item>
</category>
<category name="two">
    <item>Burger and Fries</item>
    <item>Chicken Sandwich</item>
</category>
<category name="three">
    <item>Filet of Fish</item>
    <item>Exotic Meat Stew</item>   
</category>

输出

$r1 = Array ( )
$r2 = Array ( ) 
$r3 = Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [name] => one ) [item] => Array ( [0] => Tomato and Cheese [1] => Onions [2] => Broccoli ) ) )

我可能错过了一些非常简单但被卡住的东西！

Answer 1

您应该在变量周围添加单引号

$xml = simplexml_load_string($xml);
$term = "one";
$r1 = $xml->xpath("//category[@name='$term']");
$r2 = $xml->xpath("//category[@name='" . $term . "']");
$r3 = $xml->xpath("//category[@name='one']");

echo ('$r1 = '); print_r($r1);
echo ('<br>$r2 = '); print_r($r2);
echo ('<br>$r3 = '); print_r($r3);

输出

$r1 = Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [name] => one ) [item] => Array ( [0] => Tomato and Cheese [1] => Onions [2] => Broccoli ) ) )
$r2 = Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [name] => one ) [item] => Array ( [0] => Tomato and Cheese [1] => Onions [2] => Broccoli ) ) )
$r3 = Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [name] => one ) [item] => Array ( [0] => Tomato and Cheese [1] => Onions [2] => Broccoli ) ) ) 

Answer 2

自从我使用 xpath 语法以来已经有一段时间了，但是，通过推论，它看起来像单引号的唯一区别：

以下是等价的。

$xml = simplexml_load_file("menu.xml");
$term = "one";
$r1 = $xml->xpath("//category[@name='$term']");
$r2 = $xml->xpath("//category[@name='" . $term . "']");
$r3 = $xml->xpath("//category[@name='one']");