phone number regex - need help with optional extension

[nikefido]

I have this regex:

'^\D?(\d{3})\D?\D?(\d{3})\D?(\d{4})\D?(\d{3,4})$^

for a preg_match();

 

This will test for something like 123-123-1234 1234

 

However, I want to be able to successfully test (aka, preg_math returns true) the phone number with or without an extension and with or without an "x" - for example, these should test true:

222-222-2345 x345

343 345 4567 456

123/123/1234 1234

 

Can I get some advice on making the extension "optional" (if possible) and using a letter in there as well?

[nikefido]

'^\D?(\d{3})\D?\D?(\d{3})\D?(\d{4})\D?(\D?x?\d+)?$^'