How to let regex ignore everything between brackets?

Question

Consider the following string:

I have been driving to {Palm.!.Beach:100} and it . was . great!!

I use the following regex to delete all pun

Answer 1

$str = preg_replace('(\{[^}]+\}(*SKIP)(*FAIL)|[^a-zA-Z ]+)', '', $str);

See also Split string by delimiter, but not if it is escaped.