root@topluson [~]# yum install php-mbstring
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.linux.duke.edu
 * extras: centosz3.centos.org
 * updates: centosz3.centos.org
base                                                     | 1.1 kB     00:00
extras                                                   | 2.1 kB     00:00
updates                                                  | 1.9 kB     00:00
Excluding Packages in global exclude list
Finished
Setting up Install Process
No package php-mbstring available.
Nothing to do