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From: "J.O. Aho" <user@example.net>
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Subject: Re: question about
Date: Mon, 4 Apr 2022 14:26:01 +0200
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On 23/02/2022 15.54, alex wrote:
> $ echo center | sed -E 's#(.*)#start-\1-end#'
> start-center-end
> 
> I tried to do the same thing with php, but the result is different
> 
> $ php -r "echo preg_replace('#(.*)#', 'start-\0-end', 'center') . PHP_EOL;"
> start-center-endstart--end
>                  ^^^^^^^^^^
> 
> Why?

Why I'm not sure, but figured out two solutions:

You set a number a limit to the replacement


$ php -r "echo preg_replace('#(.*)#', 'start-\1-end', 'center', 1) . 
PHP_EOL;"

or you can tell that it's from the beginning of the row

$ php -r "echo preg_replace('#^(.*)#', 'start-\1-end', 'center') . PHP_EOL;

I would guess this has to do with the end of char array \0 (internally) 
and it's counted as a white space, so it's not included in the first 
match, but then as the second match, but that is just a wild guess.

-- 

  //Aho