I have a wordpress website, and I want to add new fields when user register, like phone number and street address. 

I know how to add input fields in registration form, but I cannot understand how to save this fields in database during registration, like other details as username are saved. 

How to do that?

**UPDATE:** 

```
add_action('user_register', 'myplugin_user_register')

```

the function myplugin\_user\_register() is called after main user details like username, email was inserted in database, or all details will be saved at same time.

I also want to save extra fields in other table, in $wpdb->users, how to do this ?