php - Regex to allow numbers and only one hyphen in the middle

Question

I am trying to write a regular expression to allow numbers and only one hypen in the middle (cannot be at start or at the end) say pattern: 02-04 , 02are acceptable but pattern: -- or - or -02 or 04- or 02-04-06 are unacceptable

I tried something like this but this would allow - at the beginning and also allow multiple -

'/^[0-9 -]+$/'

I am not that good with regex so a little explanation would be real helpful.

EDIT: Sorry to bug you again with this but I need the numbers to be of only 2 digits (123-346) should be considered invalid.

Answer 1

Try this one:

/^d{1,2}(-d{1,2})?$/

One or two digits, followed by, optionally, ( a hyphen followed by one or two digits)