Regular Expressions, Checking for a range of occurrences

I have a phone number I want to match against a regular expression. The format of the phone number must match this:

(123) 123-4567 x12345

The extension is optional. Also the extension must contain 1-5 numbers. Below is a regular expression I wrote that works.

^\(\d{3}\) \d{3}-\d{4}( x\d\d?\d?\d?\d?)?$

I was wondering if there is a better way to check for the extension instead of

x\d开发者_Python百科\d?\d?\d?\d?

Can I say 1-5 occurrences of \d instead of the above some how ?

Use this :

\d{1,5}

Check Limiting Repetitions paragraph on this link for more details.

\d{1,5} will check for between 1 and 5 occurences