Regular expression: same character 3 times

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

aa => false
aaa 开发者_JS百科=> true
baaa => true
aaab => true
aaaaaab => true
baaab => true
babababa => false

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

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You can use back-references within a regex

/(.)\1\1/

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Try this regular expression:

(.)\1{2}

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This will do the job :

/(.)\1\1/