How can I add a space in string at capital letters, but keep continuous capitals together using PHP and a Regex?

Question

I want to add a space to a string on capital letters using a PHP method like preg_replace() and a regex, but I only want to add a space on the first capital letter

Answer 1

Find:

(?<!^)((?<![[:upper:]])[[:upper:]]|[[:upper:]](?![[:upper:]]))

Replace:

 $1

note the space before $1

Edit: fix.