preg_match括号模式

Question

I'm trying to change a bunch of decimals in a string to two decimal points. The regex seems to match it just fine. The problem is with the replace.

This is my code:

$input_lines = "-33.873293252 151.201538015999972,-33.873175 151.201689183999946";

print preg_replace("/[0-9]+(\.[0-9][0-9]?)?/", "$0 $2", $input_lines);

Which outputs decimal that I want | truncated decimals that I don't want :

 -33.87 3293252  151.20 1538015999972 ,-33.87 3175  151.20 1689183999946 

So I tried changing the replacement to $0 . But now the replace stopped working, and is instead giving me:

-33.873293252 151.201538015999972,-33.873175 151.201689183999946

How can I rewrite my regular expression so it gives me the desired output?

Answer 1

Better:

preg_replace("/(?<=\.\d\d)\d+/","",$input_lines);

Replaces all trailing decimals after the first two with nothing.

Answer 2

([-+]?\d+(?:\.\d{2})?)(\d*)

Try this.Replace by $1 .See demo.

https://regex101.com/r/vD5iH9/46

$re = "/([-+]?\\d+(?:\\.\\d{2})?)(\\d*)/m";
$str = "-33.873293252 151.201538015999972,-33.873175 151.201689183999946";
$subst = "$1";

$result = preg_replace($re, $subst, $str);