我想从字符串中查找段落，并格式化它们，我有什么样的作品，但它不是 100%。
所以，我有这个字符串，看起来像这样：
##Chapter 1
Once upon a time there was a little girl named sally, she went to school.
One day it was awesome!
##Chapter 2
We all had a parade!
我正在通过将##...转换为<H2>来格式化字符串，现在看起来像这样：
<h2>Chapter 1</h2>
Once upon a time there was a little girl named sally, she went to school.
One day it was awesome!
<h2>Chapter 2</h2>
We all had a parade!
现在我想将所有内容转换为一个段落，为此我这样做：
// Converts sections to paragraphs:
$this->string = preg_replace("/(^|'n'n)(.+?)('n'n|$)/", "<p>$2</p>", $this->string);
// To Remove paragraph tags from header tags (h1,h2,h3,h4,h5,h6,h7):
$this->string = preg_replace("/<p><h('d)>(.+?)<'/h'd><'/p>/i", "<h$1>$2</h$1>", $this->string);
这是最终输出（为提高可读性而添加了新行）：
<h2>Chapter 1</h2>
Once upon a time there was a little girl named sally, she went to school.
<p>One day it was awesome!</p>
<h2>Chapter 2</h2>
<p>We all had a parade!</p>
正如我在开头所说的那样，这不能 100% 工作，而且正如你所看到的，一个段落没有添加到第一段中。我可以做些什么来改进正则表达式？
你可以一步到位：
$this->string = preg_replace('~(*BSR_ANYCRLF)'R'R'K(?>[^<'r'n]++|<(?!h[1-6]'b)|'R(?!'R))+(?='R'R|$)~u',
'<p>$0</p>', $this->string);
图案详细信息
(*BSR_ANYCRLF) # 'R can be any type of newline
'R'R # two newlines
'K # reset the match
(?> # open an atomic group
[^<'r'n]++ # all characters except <, CR, LF
| # OR
<(?!h[1-6]'b) # < not followed by a header tag
| # OR
'R(?!'R) # single newline
)+ # close the atomic group and repeat one or more times
(?='R'R|$) # followed by to newlines or the end of the string
将 m switch 添加到第一个正则表达式。
// Converts sections to paragraphs:
$this->string = preg_replace("/(^|'n'n)(.+?)('n'n|$)/m", "<p>$2</p>", $this->string);
// To Remove paragraph tags from header tags (h1,h2,h3,h4,h5,h6,h7):
$this->string = preg_replace("/<p><h('d)>(.+?)<'/h'd><'/p>/i", "<h$1>$2</h$1>", $this->string);