使用正则表达式删除相同类型的html嵌套标签的最终解决方案？ [英] Final solution for using regex to remove html nested tags of the same type?

问题描述

我已经试图找到一个正则表达式的解决方案（在有人说之前：我知道我应该使用PHP DOM文档库或类似的东西，但让我们把它作为一个理论问题），寻找答案和我终于想出了在这个问题结束之前我会显示的内容。

以下是以前尝试过的很多事情的总结。 / p>

首先，我的意思是同一类型的嵌套标签是：

 任何div外的文字
< div id =my_id> bla bla 
< div> 
 bla bla bla 
< div style =some style here> 
 lalalalala 
< / div> 
< / div> 
我被困在一个div！ 
< / div> 
更多文字外面的divs 
 
< div>更多divs在这里！ 
< div id =justbeingannoying>无线电头规则< / div> 
< / div> 
  

现在想象我想使用正则表达式删除所有的div 和他们的内容 。因此，预期的结果将是：

 任何div外的文本
更多文本外部divs 
  

第一个想法将匹配所有内容。以下正则表达式与属性（style，id等）的div标签相匹配：

  /< div [^>] * >。*< \ / div> / sig 
  

当然，问题是这将匹配第一个< div和最后一个< / div>开始之间的所有，因此它将匹配更多的div外面的文本（请查看这里： https://regex101.com/r/iR8mY2/1 ），这不是我们（I）想。

这可以使用 U修饰符（Ungreedy）解决

  /< div [^>] *>。*< \ / div> / sigU 
  

但是我们会遇到比我们想要的更少的 的问题：它只匹配第一个< div直到第一个（所以，如果我们删除匹配，除了一些不匹配的标签，将会有文本我被困在一个div！，我们不想要的）。

所以，我发现一个解决方案像嵌套括号，方括号等一样的魅力：

  / \ [（[^ \ [\]] * + |（？R））* \] / si 
  pre> 
 
 
基本上，这样做是找到一个开放的方括号，然后匹配任何不是开放的或闭合的方括号*或其递归结构，找到一个关闭的方括号。
 
 
 
我现在工作的是一个坏的解决方案：基本上，首先我用一个方括号替换所有的开放标签（不能在我的代码中，由于其他原因），然后关闭方括号的结束标签，然后我使用之前的正则表达式。  
 
 
 
这件事我真的很想知道这个可能是什么只用一个正则表达式。看起来很明显，在前面的正则表达式中，使用html标签 可以使用[和]。 
但不是那么容易。问题是字符的否定（[^ .......]不适用于像div这样的字符串，似乎可以通过以下方式实现类似的功能：
 。+？（？=< div>）
  
，当然，关闭标签也是一样的
 。+？（？=< \\ \\ / div> 
  
这是或多或少的到达这个正则表达式
  /< div（（。+？（？=< \ / div>）） ;））|（？R））*< \ / div> / gis 
  
正如我之前呈现的第一个正则表达式： https://regex101.com/r / yU8pV3 / 1  
 
 
 
所以，这是我的问题：正则表达式有什么问题？
 
 
 
谢谢！
解决方案
 
免责声明
 
 
由于这个问题得到了积极的反应，我会发表一个解释你的方法是什么问题，并且将显示如何匹配不是某些特定文本的文本。
 
 
 
 不过，我想强调： 不要使用它来解析真正的任意HTML代码，因为正则表达式只能用于纯文本。  
 
 
 
您的正则表达式有什么问题
 
 
 
您的正则表达式包含< div（（。+？（？=< \ / div> ;）+。（？=< div>））|（？R））* 部分（与< div（（。+？在匹配关闭< \ / div> 部分之前< \ /？div>））|（？R））*  。当你有一些分隔的文本时，不要依赖于简单的懒惰/贪心点匹配（除非用于展开循环结构 - 当你知道你在做什么）。它是这样的：
 
 
 
 
 
 < div   - 匹配< div 由于缺少单词边界或 \s，字面上也是（<多样化 之后）
 
 
 （  - 匹配的组1：
 
 
 
 
 （。+？（？=< \ / div>）|。+？（？=< div>）） - 匹配任何1+字符（尽可能少），直到第一个< / div> 或第一个< div>  
 
 
  |  
 
 
  R）  - 重复（即插入和使用）
 
 
 
 
 
 ）* code>  - 重复第1组零次或更多次。
 
 
 
 
 
问题很清楚： 。+？（？=< \ /？div>））部分不排除匹配< div> 或< / div> ，此分支必须仅将文本NOT EQUAL与前导和后跟分隔符相匹配。
 
 
 
解决方案
 
 
 
要匹配某些特定文字以外的文字，请使用 回调贪婪令牌 。
 < div \b [^<] *>（（？：（？！< \ /？div \\ ）。+ |（？R））*< \ / div> \s * 
 ^^^^^^^^^^^^^^^^^^ 
  
请参阅 regex demo 。请注意，您必须使用DOTALL修饰符，以便能够在换行符之间匹配文本。捕获组是多余的，您可以将其删除。
 
 
 
这里重要的是（？：（？！< \ /？ div \b）。）+ 仅匹配1个或多个不是< div ....> 或< / div 序列。看到我上面链接的线程是如何工作的。
 
 
 
对于性能，温和的贪心令牌是耗资源的。解开循环技术来解决问题：
 < div \b [^<] *& [^] +（？：<（?! \ /？div \b）[^ *] * |（？R））*< \ / div> \s * 
  
请参阅这个正则表达式演示 
 
 
 
现在，令牌看起来像 [^ <] +（？：< （？！\ /？div \b）[^<] *）* ：除 之外的1+个字符     c $ c>（作为一个整体），然后再次0+非 -    s。
 
 
 
 < div \b 可能仍然在< div-tmp 中匹配，所以也许， < div（？：\s |>）是通过正则表达式来处理这个问题的更好方法。尽管如此，使用 DOM 解析HTML更容易。
 
I've been days trying to find a solution WITH regex (before somebody says it: I know I should been using the PHP DOM Document library or something alike, but let's take this as a theoretical question), looking answers up and I finally came up with what I'll show near the end of this question.

What follows is just a summary of a lot of things I've tried before.

First of all, what I mean by nested tags of the same type is:
Text outside any div
<div id="my_id"> bla bla
  <div>
  bla bla bla
    <div style="some style here">
      lalalalala
     </div>
   </div>
    I'm trapped in a div!
</div>
more text outside divs

<div>more divs here!
       <div id="justbeingannoying">radiohead rules</div>
</div>
Now imagine I want to remove all the divs and their content using regex. So the intended result would be:
Text outside any div
more text outside divs
The first idea would be matching everything. The following regex matches div tags with properties (style, id, etc):
/<div[^>]*>.*<\/div>/sig
The problem, of course, is that this will match everything between the beginning of the first "< div" and the last "< /div >", so it will match "more text outside divs" too (check here: https://regex101.com/r/iR8mY2/1 ), which is not want we (I) want.  

This could be solved using the U modifier (Ungreedy) 
/<div[^>]*>.*<\/div>/sigU
but then we'll have the problem of having less than we want: it will match only from the first "< div" till the first "" (so, if we remove the matches, besides some unmatched tags, will have the text "I'm trapped in a div!", which we don't want). 

So, I found a solution that works like a charm for nested parenthesis, square brackets, etc:
/\[([^\[\]]*+|(?R))*\]/si
Basically, what this does is finding an opening square bracket, then matching anything *that is neither an opening nor a closing square bracket * OR a recursive structure of that, finding a closing square bracket.

What I have working now is a bad solution: basically, first I replace all the opening tags with an square bracket (which can't be in my code, for other reasons), then the closing tag for a closing square bracket and then I use the previous regex. Not a very elegant solution, I know.

The thing is I really want to know how this could be done with just one regex. It seems obvious than replacing in the previous regex the "[" and the "]" by the html tags has to work. 
But is not that easy. The problem is the negation for characters ("[^.......]" doesn't work for strings like "div". It seems that something similar can be achieved by this:
.+?(?=<div>)
and, of course, the same for the closing tag
.+?(?=<\/div>
This is how, more or less, I arrived to this regex
/<div((.+?(?=<\/div>)|.+?(?=<div>))|(?R))*<\/div>/gis
Which works exactly as the first regex I presented before: https://regex101.com/r/yU8pV3/1 

So, here is my question: what is wrong with that regex? 

Thank you!
解决方案
DISCLAIMER

Since the question is met with positive reaction, I will post an answer explaining what is wrong with your approach, and will show how to match text that is not some specific text.

HOWEVER, I want to emphasize: Do not use this to parse real, arbitrary HTML code, as regex should only be used on plain text.

What is wrong with your regex

Your regex contains <div((.+?(?=<\/div>)|.+?(?=<div>))|(?R))* part (same as <div((.+?(?=<\/?div>))|(?R))*) before matching the closing <\/div> part. When you have some delimited text, do not rely on plain lazy/greedy dot matching (unless used in unroll the loop structure - when you know what you are doing). What it does is this:


<div - match <div literally (also, in <diverse due to a missing word boundary or a \s after it)
( - Group 1 that matches:


(.+?(?=<\/div>)|.+?(?=<div>)) - matches either any 1+ chars (as few as possible) up to the first </div> or to the first <div>
| 
(?R) - Recurse (i.e. insert and use)

)* - repeat Group 1 zero or more times.


The problem is clear: the (.+?(?=<\/?div>)) part does not exclude matching <div> or </div>, this branch MUST only match the text NOT EQUAL to the leading and trailing delimiters.

Solution(s)

To match text other than some specific text use a tempered greedy token.
<div\b[^<]*>((?:(?!<\/?div\b).)+|(?R))*<\/div>\s*
             ^^^^^^^^^^^^^^^^^^^ 
See the regex demo. Note you must use a DOTALL modifier so as to be able to match text across newlines.  A capturing group is redundant, you can remove it.

What is important here is that (?:(?!<\/?div\b).)+ only matches 1 or more characters that are not the starting character of a <div....> or </div sequences. See my above linked thread on how that works.

As for performance, tempered greedy tokens are resource-consuming. Unroll the loop technique comes to the rescue:
<div\b[^<]*>(?:[^<]+(?:<(?!\/?div\b)[^<]*)*|(?R))*<\/div>\s*
See this regex demo

Now, the token looks like [^<]+(?:<(?!\/?div\b)[^<]*)*: 1+ characters other than < followed with 0+ sequences of < that is not followed with /div or div (as a whole word) and then again 0+ non-<s.

<div\b might still match in <div-tmp, so perhaps, <div(?:\s|>) is a better way to deal with this via regex. Still, parsing HTML with DOM is much easier.

                        
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