Replace repeating characters with exceptions

Question

How can you translate this into Regex: Replace any char (aka '.') that is repeating more than once and replace it with one of that char with the exception of "ii" and "iii".

$reg = preg_replace('/(.)/1{1,}/','', $string);

Now this must replace VVVVV with V or .... with . and must not replace Criiid (or Criid) but Criiiiiiid with Crid.

Feel free to comment if you don't understand the question.

Answer 1

preg_replace('/([^i])\1+|(i){4,}/', '\1\2', $string)

Note that this will squeeze everything -- spaces, newlines, etc.

Answer 2

The first alternative replaces anything but i, the second alternative replaces any is which occur four times or more:

$reg = preg_replace('/([^i])\1{1,}|(i){4,}/','\1\2', $string);

Or (thanks to @Enissay):

$reg = preg_replace('/([^i])\1+|(i){4,}/','\1\2', $string);