随意用Laravel的tinker展示lookbehind功能
他需要固定长度，我们可以抓括号后的文本

原始内容为:

How fast is the car moving?
How far do you drive to work every day?

透过正规式lookbehind，只看How fast及How far后的字

(?<=How\s\w{4}\s).+|(?<=How\s\w{3}\s).+

Laravel tinker画面

php artisan tinker
Psy Shell v0.11.8 (PHP 8.1.11 X cli) by Justin Hileman
>>> $re = '/(?<=How\s\w{4}\s).+|(?<=How\s\w{3}\s).+/m';
=> "/(?<=How\s\w{4}\s).+|(?<=How\s\w{3}\s).+/m"

>>> $str = 'How fast is the car moving?
... How far do you drive to work every day?
...
... ';
=> """
   How fast is the car moving?\n
   How far do you drive to work every day?\n
   """

>>>
>>> preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
=> 2

>>>
>>> // Print the entire match result
>>> var_dump($matches);
array(2) {
  [0]=>
  array(1) {
    [0]=>
    string(18) "is the car moving?"
  }
  [1]=>
  array(1) {
    [0]=>
    string(31) "do you drive to work every day?"
  }
}

如果您想研究正规式，推^以下这个真的是「好赞」。

https://regex101.com/r/dhGbvw/1