Hey im looking for resolution to my problem at PHP. How to create regular expression which will check that I get two of the same letter from range [a-c].No matter in what order. Just about checking whether there are exactly 2.
For example i used it but it doesnt work as I want.
/a{2}b{2}c{2}/
As your last comment stated, I think you are looking for this:
^(?:([abc])\1)*$
Explaining:
^ # from start
(?: # group without saving
([abc]) # group saving in $1 one of: 'a', 'b', or 'c'
\1 # the same character saved in $1
)* # repeat it as many as possible
$ # till the end
Check live here
Use a back-reference so that it has to match the same character twice.
/([abc])\1/
Or, for multiple back-references:
/(a)\1(b)\2(c)\3/
or
/(([abc])\1)*/
(If you just need to literally match "aabbcc" then your regex should be /aabbcc/)