preg_match模式
[英]preg_match pattern
问题描述
我想创建一个适当的preg_match模式，以提取某些网页<head>的所有<link *rel="stylesheet"* /> 。 因此，此模式： #<link (.+?)>#is正常工作，直到我意识到它也捕获了<head>的<link rel="shortcut icon" href="favicon.ico" />为止。 因此，我想更改模式，以确保在链接内某处有单词样式表。 我认为它需要使用一些环顾四周，但我不确定该怎么做。 任何帮助都感激不尽。
2 个解决方案
解决方案1
2 2016-05-21 15:18:54
在这里，我们再次尝试... 不要使用正则表达式来解析html ，而应使用像PHP DOMDocument这样的html解析器 。
以下是使用方法的示例：
$html = file_get_contents("https://stackoverflow.com");
$dom = new DOMDocument();
libxml_use_internal_errors(true);
$dom->loadHTML($html);
$xpath = new DOMXpath($dom);
foreach ($xpath->query("//link[@rel='stylesheet']") as $link)
{
echo $link->getAttribute("href");
}
解决方案2
0 2016-05-22 16:28:00
要使用正则表达式执行此操作，最好将其分为两部分进行操作，第一部分是将头部与身体分开，以确保您仅在头部内工作。
然后第二部分将解析头部以查找所需的链接
解析链接
<link\\s*(?=(?:[^>=]|='[^']*'|="[^"]*"|=[^'"][^\\s>]*)*?rel=['"]?stylesheet)(?:[^>=]|='(?:[^']|\\\\')*'|="(?:[^"]|\\\\")*"|=[^'"][^\\s>]*)*\\s*>
该表达式将执行以下操作：
- 找到所有的
<link标签 - 确保链接标记具有所需的属性
rel='stylesheet - 允许属性值具有单引号，双引号或不带引号
- 避免HTML解析警察大喊大叫的混乱且困难的情况
例
现场演示
https://regex101.com/r/hC5dD0/1
示范文本
注意最后一行中的困难边缘情况。
<link *rel="stylesheet"* />
<link rel="shortcut icon" href="favicon.ico" />
<link onmouseover=' rel="stylesheet" ' rel="shortcut icon" href="favicon.ico">
比赛样本
<link *rel="stylesheet"* />
说明
NODE EXPLANATION
----------------------------------------------------------------------
<link '<link'
----------------------------------------------------------------------
\s* whitespace (\n, \r, \t, \f, and " ") (0 or
more times (matching the most amount
possible))
----------------------------------------------------------------------
(?= look ahead to see if there is:
----------------------------------------------------------------------
(?: group, but do not capture (0 or more
times (matching the least amount
possible)):
----------------------------------------------------------------------
[^>=] any character except: '>', '='
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
=' '=\''
----------------------------------------------------------------------
[^']* any character except: ''' (0 or more
times (matching the most amount
possible))
----------------------------------------------------------------------
' '\''
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
=" '="'
----------------------------------------------------------------------
[^"]* any character except: '"' (0 or more
times (matching the most amount
possible))
----------------------------------------------------------------------
" '"'
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
= '='
----------------------------------------------------------------------
[^'"] any character except: ''', '"'
----------------------------------------------------------------------
[^\s>]* any character except: whitespace (\n,
\r, \t, \f, and " "), '>' (0 or more
times (matching the most amount
possible))
----------------------------------------------------------------------
)*? end of grouping
----------------------------------------------------------------------
rel= 'rel='
----------------------------------------------------------------------
['"]? any character of: ''', '"' (optional
(matching the most amount possible))
----------------------------------------------------------------------
stylesheet 'stylesheet'
----------------------------------------------------------------------
) end of look-ahead
----------------------------------------------------------------------
(?: group, but do not capture (0 or more times
(matching the most amount possible)):
----------------------------------------------------------------------
[^>=] any character except: '>', '='
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
=' '=\''
----------------------------------------------------------------------
(?: group, but do not capture (0 or more
times (matching the most amount
possible)):
----------------------------------------------------------------------
[^'] any character except: '''
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
\\ '\'
----------------------------------------------------------------------
' '\''
----------------------------------------------------------------------
)* end of grouping
----------------------------------------------------------------------
' '\''
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
=" '="'
----------------------------------------------------------------------
(?: group, but do not capture (0 or more
times (matching the most amount
possible)):
----------------------------------------------------------------------
[^"] any character except: '"'
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
\\ '\'
----------------------------------------------------------------------
" '"'
----------------------------------------------------------------------
)* end of grouping
----------------------------------------------------------------------
" '"'
----------------------------------------------------------------------
| OR
----------------------------------------------------------------------
= '='
----------------------------------------------------------------------
[^'"] any character except: ''', '"'
----------------------------------------------------------------------
[^\s>]* any character except: whitespace (\n,
\r, \t, \f, and " "), '>' (0 or more
times (matching the most amount
possible))
----------------------------------------------------------------------
)* end of grouping
----------------------------------------------------------------------
\s* whitespace (\n, \r, \t, \f, and " ") (0 or
more times (matching the most amount
possible))
----------------------------------------------------------------------
> '>'
----------------------------------------------------------------------
preg_match的模式
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