PHP regex to match Windows product key

Question

I am attempting (and failing) to write a PHP regex that will match a Windows product key in the form XXXXX-XXXXX-XXXXX-XXXXX-XXXXX (where X is an uppercase letter or a number).

I have come up with the following, but it is not doing quite what I expect (provided it actually can do what I expect!). I consider myself pretty well versed in PHP, but regexes are a particular weak point for me.

([A-Z1-9]{5})-([A-Z1-9]{5})-([A-Z1-9]{5})-([A-Z1-9]{5})-([A-Z1-9]{5})

What I am actually after is it to pass ABCDE-FGHIJ-KLMNO-PQRST-UVWXY but to fail ABCDE-FGHIJ-KLMNO-PQRST-UVWXYZ (notice the last block has 6 characters).

Bonus chatter: Yes, I know that not all letters are valid in a Windows product key, but the important bit is that it validates the text has been entered in the correct format.

Answer 1

All you're missing is position anchors in your regex. Currently, the regex will match that pattern anywhere in a string. The string could by "my product key is XXXXX-XXXXX-XXXXX-XXXXX-XXXXX and my name is Bob" and your regex would match. What you need is

^([A-Z1-9]{5})-([A-Z1-9]{5})-([A-Z1-9]{5})-([A-Z1-9]{5})-([A-Z1-9]{5})$

The ^ matches only the beginning of the string and $ matches only the end.