递归正则表达式来处理由{|括起来的嵌套字符串和|} [英] recursive regular expression to process nested strings enclosed by {| and |}

问题描述

在一个项目中，我有一个带有类似模式的文本:

In a project I have a text with patterns like that:

{|文字{|文字|}文字|}
更多文字

{| text {| text |} text |}
more text

我想用括号括起来的第一部分.为此，我递归使用preg_match.下面的代码已经可以正常工作了:

I want to get the first part with brackets. For this I use preg_match recursively. The following code works fine already:

preg_match('/\{((?>[^\{\}]+)|(?R))*\}/x',$text,$matches);

但是，如果我添加符号"|"，则会得到一个空结果，并且我不知道为什么:

But if I add the symbol "|", I got an empty result and I don't know why:

preg_match('/\{\|((?>[^\{\}]+)|(?R))*\|\}/x',$text,$matches);

我无法使用第一个解决方案，因为在文本中也可能存在类似{text}的内容.有人可以告诉我我在这里做错了什么吗?谢谢

I can't use the first solution because in the text something like { text } can also exist. Can somebody tell me what I do wrong here? Thx

推荐答案

尝试一下:

'/(?s)\{\|(?:(?:(?!\{\||\|\}).)++|(?R))*\|\}/'

在原始正则表达式中，您使用字符类[^{}]来匹配除定界符之外的所有内容.当分隔符仅是一个字符，而您的分隔符是两个字符时，这很好.要不匹配多字符序列，您需要执行以下操作:

In your original regex you use the character class [^{}] to match anything except a delimiter. That's fine when the delimiters are only one character, but yours are two characters. To not-match a multi-character sequence you need something this:

(?:(?!\{\||\|\}).)++

点匹配任何字符(包括换行符，感谢(?s))，但仅在先行确定它不属于{|或|}序列的一部分之后.我还删除了原子组((?>...))，并用所有格修饰符(++)替换了它，以减少混乱.但是您绝对应该在正则表达式的该部分中使用另一个，以防止灾难性回溯.

The dot matches any character (including newlines, thank to the (?s)), but only after the lookahead has determined that it's not part of a {| or |} sequence. I also dropped your atomic group ((?>...)) and replaced it with a possessive quantifier (++) to reduce clutter. But you should definitely use one or the other in that part of the regex to prevent catastrophic backtracking.

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