A comprehensive regex for phone number validation

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:

• 1-234-567-8901


• 1-234-567-8901 x1234


• 1-234-567-8901 ext1234


• 1 (234) 567-8901


• 1.234.567.8901


• 1/234/567/8901


• 12345678901

I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.

Answer

Better option... just strip all non-digit characters on input (except 'x' and leading '+' signs), taking care because of the British tendency to write numbers in the non-standard form +44 (0) ... when asked to use the international prefix (in that specific case, you should discard the (0) entirely).

Then, you end up with values like:

 12345678901
 12345678901x1234
 345678901x1234
 12344678901
 12345678901

 12345678901
 12345678901
 +4112345678
 +441234567890

Then when you display, reformat to your hearts content. e.g.

  1 (234) 567-8901
  1 (234) 567-8901 x1234