O php-mbstrings está disponível no RHEL7 através do canal rhel-x86_64-server-optional-7.
rhn-channel -c rhel-x86_64-server-optional-7 -a; yum info php-mbstrings
yum info php-mbstring
Loaded plugins: rhnplugin
This system is receiving updates from RHN Classic or Red Hat Satellite.
epel/x86_64/metalink | 4.3 kB 00:00:00
Installed Packages
Name : php-mbstring
Arch : x86_64
Version : 5.4.16
Release : 21.el7
Size : 1.3 M
Repo : installed
From repo : rhel-x86_64-server-optional-7
Summary : A module for PHP applications which need multi-byte string handling
URL : http://www.php.net/
License : PHP and LGPLv2 and BSD and OpenLDAP
Description : The php-mbstring package contains a dynamic shared object that will add
: support for multi-byte string handling to PHP.