How to find all characters in string "abaabaaabaabaaaa" except substring "aa"?

Question

Regular Expressions

Hello. Suppose there is a string "abaabaaabaabaaaa", how to find all the characters in it, except for the substring "aa"?
The result should be " ab aa baaab aa baaaa ".
I managed to do the opposite. Find an occurrence of "aa" regex101 .

Answer 1

$str = 'abaabaaabaabaaaa';
$out = preg_split('~(?<!a)aa(?!a)~', $str, -1, PREG_SPLIT_NO_EMPTY);
print_r($out);