Regex to check a valid number in a format in PHP

Question

I want to check if the string is in the following format

1. YYMMDD-XXXX
2. YYYYMMDD-XXXX
3. YYMMDDXXXX
4. YYYYMMDDXXXX

I have this regex

^\d{6,8}(-\d{4})?$

But then I am stuck. I am really new at regex. Can I get some help or some pointers?

Answer 1

Make the - optional and your regex works:

^\d{6,8}(-?\d{4})?$

https://regex101.com/r/uoF1HM/1/

This also would match many number formats though. Your example strings look like dates, if that is the case I'd use something stricter ( or already written eg https://stackoverflow.com/a/14566624/3783243 might be a good place to start).

Answer 2

You can use this function:

function checkFunc($value){
  if (preg_match('/^[0-9]{6,8}(-?)[0-9]{4}$/', $value)) {
    //is valid
     return $value;
  } else {
    //is invalid
    return false;
 }
}

echo checkFunc("20180529-4444"); //20180529-4444

but for the first part of string, you will have to create different check for the date format

Answer 3

In your regex ^\\d{6,8}(-\\d{4})?$ youy have an optional group (-\\d{4})? with a hyphen inside the group. That means that you can only match a format like \\d{6,8} or with a hyphen \\d{6,8}-\\d{4} but not \\d{6,8}\\d{4} because the hyphen should be there according to the optional group.

If you want to match your values without any capturing groups you could make only the dash optional ?

That would match

• ^ Assert position at the start of the line
• \\d{6,8} Match 6 - 8 digits
• -? Match optional dash
• \\d{4} Match 4 digits

• $ Assert position at the end of the line

  ^\\d{6,8}-?\\d{4}$