Add the appropriate repository:

# rpm -ivh http://www.mirrorservice.org/sites/dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

 

Update the server:

# yum update

 

Now, PHP MCrypt can be installed using yum:

# yum install php-mcrypt

 

Restart Apache for the update to take effect:

# service httpd restart