RHEL Yum
From Hawk Wiki
Yum Management
By default, Redhat repo does not contain php-mbstring in Amazon AWS. php-mbstring is required for phpMyAdmin, wordpress, etc.
To Install php-mbstring
yum repolist all # found rhui-REGION-rhel-server-optional in the list yum-config-manager --enable rhui-REGION-rhel-server-extras rhui-REGION-rhel-server-optional yum search php- yum install php-mbstring