PHP XPath 选择最后一个匹配元素
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PHP XPath selecting last matching element
提问by deab
Possible Duplicates:
PHP SimpleXML. How to get the last item?
XSLT Select all nodes containing a specific substring
I need to find the contents of the last span element with a class of 'myClass'. I've tried various combinations but can't find the answer.
我需要找到具有“myClass”类的最后一个 span 元素的内容。我尝试了各种组合，但找不到答案。
//span[@class='myPrice' and position()=last()]
This returns all the elements with class 'myClass', I'm guessing this is because each found element is the last at the time of processing - but I just need the actual last matching element.
这将返回具有“myClass”类的所有元素，我猜这是因为每个找到的元素都是处理时的最后一个元素 - 但我只需要实际的最后一个匹配元素。
回答by VolkerK
You have to mark for the processor that you want to treat //span[@class='myPrice']as the current set and then apply the predicate position()=last() to that set.
您必须标记要//span[@class='myPrice']视为当前集合的处理器，然后将谓词 position()=last() 应用于该集合。
(//span[@class='myPrice'])[last()]
e.g.
例如
<?php
$doc = getDoc();
$xpath = new DOMXPath($doc);
foreach( $xpath->query("(//span[@class='myPrice'])[last()]") as $n ) {
echo $n->nodeValue, "\n";
}
function getDoc() {
$doc = new DOMDOcument;
$doc->loadxml( <<< eox
<foo>
<span class="myPrice">1</span>
<span class="yourPrice">0</span>
<bar>
<span class="myPrice">4</span>
<span class="yourPrice">99</span>
</bar>
<bar>
<span class="myPrice">9</span>
</bar>
</foo>
eox
);
return $doc;
}
回答by Michael Kay
The expression you used means "select every span element provided that (a) it has @class='myprice', and (b) it is the last child of its parent. There are two errors:
您使用的表达式的意思是“选择每个 span 元素，前提是 (a) 它具有@class='myprice'，并且 (b) 它是其父级的最后一个子级。有两个错误：
(1) you need to apply the filter [position()=last()]after filtering by @class, rather than applying it to all span elements
(1) 需要[position()=last()]通过@class过滤后应用过滤器，而不是应用到所有span元素
(2) an expression of the form //span[last()]means /descendant-or-self::*/(child::span[last()])which selects the last child span of every element. You need to use parentheses to change the precedence: (//span)[last()].
(2) 形式的表达//span[last()]意味着/descendant-or-self::*/(child::span[last()])选择每个元素的最后一个子跨度。您需要使用括号来更改优先级： (//span)[last()].
So the expression becomes (//span[@class='myPrice'])[last()]as given by VolkerK.
所以表达式变成(//span[@class='myPrice'])[last()]了 VolkerK 给出的。
