I want regex to match a pattern that can only have either two alphabet characters or numeric characters

Question

I want a regex for PHP that can match two alphabetic characters or two numeric characters. For example:

AB or 45

The characters can't be mixed with alphabetic and numeric.

^(\w)\1|[A-Z|0-9]{2}$

I used the above regex but it doesn't work correctly.

For something so simple, regex seems to be an overkill for me. — nice_dev, Aug 05 '19 at 11:25

Wiktor Stribiżew · Accepted Answer · 2019-08-05T11:20:03.667

1

You may use

preg_match('~^(?:[A-Za-z]{2}|\d{2})$~', $s, $match)

The ^(?:[A-Za-z]{2}|\d{2})$ pattern matches two ASCII letters or two ASCII digits.

Details

^ - start of string
(?:[A-Za-z]{2}|\d{2}) - a non-capturing group matching either
- [A-Za-z]{2} - two ASCII letters
- | - or
- \d{2} - two digits
$ - end of string.

To make it match all Unicode letters, you may use

preg_match('~^(?:\p{L}{2}|[0-9]{2})$~u', $s, $match)

edited Aug 05 '19 at 11:20

answered Aug 05 '19 at 11:15

Wiktor Stribiżew

What does `?:` mean here? – dumbPotato21 Aug 05 '19 at 11:20
1

@ImaginaryPumpkin See https://stackoverflow.com/questions/3512471/what-is-a-non-capturing-group-in-regular-expressions – Wiktor Stribiżew Aug 05 '19 at 11:20
@WiktorStribiżew My bad. The string itself is the entire captured thing and maybe you used `?:` for performance reasons. – nice_dev Aug 05 '19 at 11:32
1

@vivek_23 Just best practice and force of habit. – Wiktor Stribiżew Aug 05 '19 at 11:32

1 Answers1