如何使用正则表达式解析此HTML？
[英]How can I parse this HTML with a regular expression?
问题描述
I am trying to write a regular expression to extract the href and anchor text of a list of URLs from an HTML source. 
我正在尝试编写一个正则表达式，以从HTML源中提取URL列表的href和anchor文本。 The anchor text can be any values. anchor文本可以是任何值。
The HTML part goes as follow: HTML部分如下：
<div class="links"><a rel="nofollow" target="_blank" href="http://url1.com" class="get-all">URL1</a><a rel="nofollow" target="_blank" href="http://url2.com" class="get-all">This is Url-2</a><a rel="nofollow" target="_blank" href="http://url3.com" class="get-all">This is Url-3</a><a rel="nofollow" target="_blank" href="http://url4.com" class="get-all">Sweet URL 4</a></div>
I tried the following regular expression, but it's not working since it grabs everything before the </a> tag and fails. 我尝试了以下正则表达式，但由于</a>标记之前的所有内容</a>并失败，因此它无法正常工作。
preg_match_('/<a rel="nofollow" target="_blank" href="(.*)" class="see-all">(.*)<\/a>/', $source , $website_array);
What would be a working regular expression to extract my required data? 提取所需数据的有效正则表达式是什么？
4 个解决方案
解决方案1
6 已采纳 2013-02-19 23:15:57
If you must know, the expression is greedy, so it will likely match the start of the first anchor and the end of the last; 如果您必须知道，该表达式是贪婪的，因此它很可能与第一个锚点的开始和最后一个锚点的结束匹配； the /U modifier will fix that: /U修饰符可以解决以下问题：
preg_match('/<a rel="nofollow" target="_blank" href="(.*)" class="see-all">(.*)<\/a>/U', $source , $website_array);
Note that pcre.backtrack_limit applies to ungreedy mode. 请注意pcre.backtrack_limit适用于非贪婪模式。
Using look-ahead sets might give better performance: 使用预读集可能会提供更好的性能：
preg_match('/<a rel="nofollow" target="_blank" href="([^"]*)" class="see-all">([^<]*)<\/a>/', $source , $website_array);
This will have trouble with tags inside the anchor itself. 这将对锚自身内部的标签造成麻烦。
With aforementioned limitations, I would seriously consider using a HTML parser: 由于上述限制，我将认真考虑使用HTML解析器：
$d = new DOMDocument;
$d->loadHTML($source);
$xp = new DOMXPath($d);
foreach ($xp->query('//a[@class="see-all"][@rel="nofollow"][@target="_blank"]') as $anchor) {
$href = $anchor->getAttribute('href');
$text = $anchor->nodeValue;
}
This would happily handle the attributes in a different order and give you the ability to query further inside, etc. 这将以不同的顺序愉快地处理属性，并使您能够在内部进行进一步查询，等等。
解决方案2
2 2013-02-19 23:16:30
Try 尝试
preg_match_all('/<a[^>]+href="([^"]+)"[^>]*>([^>]+)<\/a>/is', $source , $website_array);
it will match all links and return an array with info. 它将匹配所有链接并返回包含信息的数组。 Notes: 笔记：
[^"] - matches any character except " [^“]-匹配除“
解决方案3
1 2013-02-19 23:18:21
While parsing HTML with regex is generally a bad idea (I would suggest looking at DOMDocument class for better solution), it can be used in some cases where you have a VERY specific idea of what you are trying to extract and can be assured that in all cases, that variable text won't actually break your regex. 虽然使用regex解析HTML通常不是一个好主意（我建议您看一下DOMDocument类以获得更好的解决方案），但是在某些情况下，如果您对要提取的内容有非常特定的想法，可以放心使用它，并且可以确保在在所有情况下，该可变文本实际上都不会破坏您的正则表达式。
For your case, you might try: 对于您的情况，您可以尝试：
$pattern = '#<a rel="nofollow" target="_blank" href="(.*)" class="get-all">(.*)</a>#U';
preg_match_all($pattern, $source, $website_array);
Note the ungreedy modifier ( U ) at the end. 请注意最后的非贪婪修饰符（ U ）。 That is very important to only match the smallest match possible. 仅匹配最小匹配项非常重要。
解决方案4
0 2013-02-19 23:24:39
Alternatively you can do it like this: 另外，您也可以这样：
<?php
$html = <<<HTML
<div class="links"><a rel="nofollow" target="_blank" href="http://url1.com" class="get-all">URL1</a><a rel="nofollow" target="_blank" href="http://url2.com" class="get-all">This is Url-2</a><a rel="nofollow" target="_blank" href="http://url3.com" class="get-all">This is Url-3</a><a rel="nofollow" target="_blank" href="http://url4.com" class="get-all">Sweet URL 4</a></div>
HTML;
$xml = new DOMDocument();
@$xml->loadHTML($html);
$links=array();
$i=0;
//Get all divs
foreach($xml->getElementsByTagName('div') as $divs) {
//if this div has a class="links"
if($divs->getAttribute('class')=='links'){
//loop through this div
foreach($xml->getElementsByTagName('a') as $a){
//if this a tag dose not have a class="get-all" continue to next
if($a->getAttribute('class')!='get-all')
continue;
//Assign values to the links array
$links[$i]['href']=$a->getAttribute('href');
$links[$i]['value']=$a->nodeValue;
$i++;
}
}
}
print_r($links);
/*
Array
(
[0] => Array
(
[href] => http://url1.com
[value] => URL1
)
[1] => Array
(
[href] => http://url2.com
[value] => This is Url-2
)
[2] => Array
(
[href] => http://url3.com
[value] => This is Url-3
)
[3] => Array
(
[href] => http://url4.com
[value] => Sweet URL 4
)
)
*/
?>
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.