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 ~]#