manuelh
commented
11 years ago This was to support anyone writing phone numbers with the plus (+) sign for international calls.
For example, a German phone number could be written with the country prefix being 0049 or +49
To prevent people entering random text, I would probably suggest a regex to check the validity.
More info on regex here: http://stackoverflow.com/questions/2113908/what-regular-expression-will-match-valid-international-phone-numbers
Example from Answer # 2 :
\+(9[976]\d|8[987530]\d|6[987]\d|5[90]\d|42\d|3[875]\d|
2[98654321]\d|9[8543210]|8[6421]|6[6543210]|5[87654321]|
4[987654310]|3[9643210]|2[70]|7|1)\d{1,14}$
When editing my profile details, I am allowed to add text to the Mobile and Business number fields. Only numbers should be allowed in these input boxes.