To install Mycrpyt (at least how I do it) is pretty easy if you are using Yum (http://www.keithdmitchell.com/?tag=yum-install).

To do so, simply type thefollowing once you have shelled into your vps:

# yum install php-mcrypt

You will also need to install the mhash kit:

#yum install php-mhash.

That’s it.