PHP regex: remove all chars from start and end

Question

The aim is to remove all starting and ending from a string. There can be none, one and many at the start and end, independently in number.

I thought on using preg_replace with a regex expression. But the following test is not working:

$text = "asd
asd
asd
asd
";
//$text = "

asd
asd
asd
asd
";
$text = preg_replace('/^(\n)*(?!\n)(.*)(?<!\n)(\n)*$/', '$2', $text);
var_dump($text);

With regex101.com the group 2 (see $2 above) is exactly the middle of the string, without starting and ending .

Questions:

1. What is wrong with my PHP code above? Why can't I replace the full text with only the middle part? Should I really remove start/end and not replacing with the middle part?
2. When I use the regex expression /^(\n)*(.*)(\n)*$/ instead of the one given above, do I have any disadvantage? In the regex expression above I try "start with - any char except - any char wanted but not end with - end with ". And in the shorter expression I just list none, one or many at start and end. But could this be a problem, that e.g. only one of many at start/end will be replaced and some will not be replaced? Is there a guarantee, that a will not be part of the (.*) in the middle?

EDIT with solution

1. solution: this basic example would also be possible to solve with the PHP trim function. (In my case the preg_replace had a special reason, so for me this answer from ryszard-czech worked)
2. attention: the string $text must be with double quotes " and not with single quotes ' because there is a significant difference in PHP!

question from:https://stackoverflow.com/questions/65602538/php-regex-remove-all-chars-from-start-and-end

Answer 1

Use

$text = preg_replace('/^
+|
+z/', '', $text);

Explanation

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  
+                      '
' (newline) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
 |                        OR
--------------------------------------------------------------------------------
  
+                      '
' (newline) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
  z                       the end of the string