If you need to install ionCube loader on Centos 6.4 you will need either to enable Atomic repository on your Linux box or to download their SRPM package and rebuild it.
Way 1
wget -q -O - http://www.atomicorp.com/installers/atomic |sh
yum install php-ioncube-loader
Way 2
rpm -ivh rpmbuild/RPMS/x86_64/php-ioncube-loader-4.2.2-2.art.x86_64.rpm
rpmbuild -bb ~/rpmbuild/SPECS/php-ioncube-loader-art.spec
rpm -ivh rpmbuild/RPMS/x86_64/php-ioncube-loader-4.2.2-2.art.x86_64.rpm
Checking:
[root@sched ~]# php -v PHP 5.4.13 (cli) (built: Mar 14 2013 08:57:49) Copyright (c) 1997-2013 The PHP Group Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies with the ionCube PHP Loader v4.2.2, Copyright (c) 2002-2012, by ionCube Ltd. [root@sched ~]#