How to add country code after user insert their mobile number

[soundsticks]

How to add country code if user doesn't enter the country code when they register? If user did enter the country code it will skip and store it into database, if user doesn't enter then system will add the country code and store to database. How can I do that? 

[haku]

How do you intended to determine their country code if they don't enter one?

[soundsticks]

I have done in this way.

if (preg_match('/^01/', $_POST['mobile']))
{
...
}
elseif (preg_match('/^60/', $_POST['mobile'])) 
{
...
}