Regular expression: same character 3 times

Question

I want a regular expression (in php) to this (same character 3 times):

aa => false
aaa => true
baaa => true
aaab => true
aaaaaab => true
baaab => true
babababa => false

For any character, not only 'a' and 'b'.

Answer 1

You can use back-references within a regex

/(.)\1\1/

Answer 2

Try this regular expression:

(.)\1{2}