Regular expressions, allow specific format only. "John-doe" - php

Question

I've researched a little, but I found nothing that relates exactly to what I need and whenever tried to create the expression it is always a little off from what I require.
I attempted something along the lines of [AZaz09]{3,8}\-[AZaz09]{3,8}.
I want the valid result to only allow text-text, where either or the text can be alphabetical or numeric however the only symbol allowed is - and that is in between the two texts.
Each text must be at least three characters long ({3,8}?), then separated by the -.
Therefore for it to be valid some examples could be:
Text-Text
Abc-123
123-Abc
A2C-def4gk
Invalid tests could be:
Ab-3
Abc!-ajr4
a-bc3-25aj
a?c-b%

Answer 1

You need to use anchors and use the - so the characters in the character class are read as a range, not the individual characters.
Try:
^[A-Za-z0-9]{3,8}-[A-Za-z0-9]{3,8}$
Demo: https://regex101.com/r/xH3oM8/1
You also could simplify it a but with the i modifier and the \d meta character.
(?i)^[a-z\d]{3,8}-[a-z\d]{3,8}$

Answer 2

If accented letters should be allowed, or any other letter that exists in the Unicode range (like Greek or Cyrillic letters), then use the u modifier (for UTF-8 support) and \pL to match Unicode letters (and \d for digits):
$string ="
Mañana-déjà
Text-Text
Abc-123
123-Abc
A2C-def4gk
Ab-3
Abc!-ajr4
a-bc3-25aj
a?c-b%";
$regex='/^[\pL\d]{3,}-[\pL\d]{3,}$/mu';
preg_match_all($regex, $string, $matches);
var_export($matches);
Output:
array (
0 =>
array (
0 => 'Mañana-déjà',
1 => 'Text-Text',
2 => 'Abc-123',
3 => '123-Abc',
4 => 'A2C-def4gk',
),
)
NB: the difference with \w is that [\pL\d] will not match an underscore.

Answer 3

You could come up with the following:
<?php
$string ="
Text-Text
Abc-123
123-Abc
A2C-def4gk
Ab-3
Abc!-ajr4
a-bc3-25aj
a?c-b%";
$regex='~
^\w{3,} # at last three word characters at the beginning of the line
- # a dash
\w{3,}$ # three word characters at the end of the line
~xm'; # multiline and freespacing mode (for this explanation)
# ~xmu for accented characters
preg_match_all($regex, $string, $matches);
print_r($matches);
?>
As #chris85 pointed out, \w will match an underscore as well. Trincot had a good comment (matching accented characters, that is). To achieve this, simply use the u modifier.
See a demo on regex101.com and a complete code on ideone.com.

Answer 4

You can use this regex
^\w{3,}-\w{3,}$
^ // start of the string
\w{3,} // match "a" to "z", "A" to "Z" and 0 to 9 and requires at least 3 characters
- // requires "-"
\w{3,} // same as above
$ // end of the string
Regex Demo

Answer 5

And a short one.
^([^\W_]{3,8})-(?1)$
[^\W_] can be used as short for alnum. It subtracts the underscore from \w
(?1) is a subroutine call to the pattern in first group
Demo at regex101
My vote for #chris85 which is most obvious and performant.

Answer 6

This one
^([\w]{3,8}-[\w]{3,8})$
https://regex101.com/r/uS8nB5/1