php71 to mariadb 5.5.56

I have php71 install on rel 7.4 with 5.5.56-MariaDB MariaDB Server
I am trying to configure php71 to connet to Mariadb.

mysql_select_db($dbname, $connection);
does not work

Here is out php info:
http://tritechsc.ksd.org/test.php

additionally
phpMyAdmin - Error

The mbstring extension is missing. Please check your PHP configuration.