PHP Pattern Validation

Question

I'm having a bit of trouble getting my pattern to validate the string entry correctly. The PHP portion of this assignment is working correctly, so I won't include that here as to make this easier to read. Can someone tell me why this pattern isn't matching what I'm trying to do?

This pattern has these validation requirements:

1. Should first have 3-6 lowercase letters
2. This is immediately followed by either a hyphen or a space

3. Followed by 1-3 digits

   $codecheck = '/^([[:lower:]]{3,6}-)|([[:lower:]]{3,6} ?)\d{1,3}$/';
   

Currently this catches most of the requirements, but it only seems to validate the minimum character requirements - and doesn't return false when more than 6 or 3 characters (respectively) are entered.

Thanks in advance for any assistance!

Answer 1

The problem here lies in how you group the alternatives. Right now, the regex matches a string that

• ^([[:lower:]]{3,6}-) - starts with 3-6 lowercase letters followed with a hyphen
• | - or
• ([[:lower:]]{3,6} ?)\d{1,3}$ - ends with 3-6 lowercase letters followed with an optional space and followed with 1-3 digits.

In fact, you can get rid of the alternation altogether:

$codecheck = '/^\p{Ll}{3,6}[- ]\d{1,3}$/';

See the regex demo

Explanation:

• ^ - start of string
• \p{Ll}{3,6} - 3-6 lowercase letters
• [- ] - a positive character class matching one character, either a hyphen or a space
• \d{1,3} - 1-3 digits
• $ - end of string

Answer 2

You need to delimit the scope of the | operator in the middle of your regex.

As it is now:

• the right-side argument of that OR runs up until the very end of your regex, even including the $. So the digits, nor the end-of-string condition do not apply for the left side of the |.

• the left-side argument of the OR starts with ^, and only applies to the left side.

That is why you get a match when you supply 7 lowercase characters. The first character is ignored, and the rest matches with the right-side of the regex pattern.