How to Validate a phone number with '+' sign in beginning?

Question

hi All

I want to Validate a phone number with '+' sign in beginning.

If user enter number like 9876543210. 

I should append a '+' sign in beginning and save that value.

If user enter number like [phone]. 

Allow to Save the Value.

No special char,a-z,A-Z  is allowed.

Thanks in advance

Anurag