正则表达式查找和表达并插入到中间答案

【问题标题】：Regex to find and expression and insert into the middle正则表达式查找和表达并插入到中间
【发布时间】：2021-03-21 19:00:09
【问题描述】：

我会尽量简短。我正在尝试使用 preg_replace 的正则表达式来查找数字，但我想非破坏性地编辑字符串。

一个例子：（尽管由于数据保护，这是一个近似值）

$subject_string = 'section 1.1: Disability ........' ;
$outcome = preg_replace( '/$section[\d.\d]+/' ,  '\<hr/\>'  , $subject_string );
// $outcome will be: "\<hr/\>section 1.1: Disability ........"

任何帮助将不胜感激

【问题讨论】：

标签： php regex preg-replace

【解决方案1】：

使用

\bsection\s*\d+(?:\.\d+)*:

替换为<hr/>$0。见regex proof。

解释

--------------------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
--------------------------------------------------------------------------------
  section                  'section'
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (0 or more times
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    \.                       '.'
--------------------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
  )*                       end of grouping
--------------------------------------------------------------------------------
  :                        ':'

代码 sn-p：

$re = '/\bsection\s*\d+(?:\.\d+)*:/';
$str = 'section 1.1: Disability ........';
$subst = '<hr/>$0';
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;

【讨论】：

这太棒了，优雅！谢谢！理解正则表达式还有很长的路要走。在这里，捕获和反向引用是我缺少的关键！