integrate libphonenumber with codeigniter as a library using this library you will know How to validate phone_number using PHP using codeigniter
1- add the library into libraries directory
2- add valid_mob into third_party directory
3- copy is_valid_mobile function into your controller
that's it :) .
the full tutorial is here http://webeasystep.com/blog/view_article/How_to_validate_phone_number_using_PHP