install RHEL 6.5 php package on RHEL 5.10?

Is it advisable to install a php package targeted to RHEL 6.5 to RHEL 5.10? What is the risk?
php inoperative, server OS inoperative?
I have a subscribed RHEL 6.5 server I can use yumdownloader on to get the php packages.
I have a RHEL 5.10 server on a disconnected network and need to update php.
OR is there a way to use yumdownloader on the 6.5 server to download the 5.10 php packages?
I need to update due to vulnerabilities present in the current 5.10 php install.

Thanks for any help.