如何用逗号替换点，但仅用字符串中的数字？ （PHP）

I want to replace all dots in a string to commas, but only for numbers (in PHP):

Like :

this is. an example. 15.68€

and it should be converted to something like this is. an example. 15,68€

Is there an easy preg_replace or any other option ?

Try this one

  $str = "this is. an example. 15.68€";
  function cleaner($matches)
   {
     return str_replace("." , "," , $matches["nrs"]);
   }

 $str = preg_replace_callback ("/(?P<nrs>[0-9]+.[0-9]+)/" , "cleaner" , $str);
 echo $str;

I have used preg_replace_callback. The behavior of this function is almost identical to preg_replace(), except for the fact that instead of replacement parameter, one should specify a callback. Check for more about it here. You can also test the live preview of my solution.