Laravel validation for this number +852 1111 2222?
Regular expression will be good example for you as you the format of phone number won't change you cant take this regex patter as example
'phone_number' => 'required|regex:/^\+\d{3}\s\d{4}\s\d{4}$/',
In case the phone number prefix doesn't change you can include it directly in the pattern like this
'phone_number' => 'required|regex:/^\+852\s\d{4}\s\d{4}$/',
Here is the link to regex101