installing PHP-MSSQL in centOS6.2

download and install the Epel rpm that contains the correct packages
rpm -Uvh 'http://download.fedoraproject.org/pub/epel/6/i386/epel-release6-5.noarch.rpm'

configuation file for the Epel rpm in the yum.repos.d directory

vi /etc/yum.repos.d/epel.repo

Change "enabled=1" to "enabled=0"

and then
yum install php-mssql --enablerepo=epel

restart your httpd service indeed.