php version 5.1.6 needed miimum 5.2.1

hello
i followed exactlly the "Perfect server centos 5.2" tutorial, everything is working perfect so far, it s just that i tryed to install a php website on my domain, and when getting to the checks , on of the errors was

Version Checks
PHP Version
Minimum Version: v5.2.1
Version Found: v5.1.6 Failed
Please update php to the latest version in the v5.2 code branch

if i m trying to install php again, will be there any problems besides rewriting the lines from the tutorial ??

for the specified web domain i have set only php ... if i set su-php will this problem with checking will be solvrd ?? i m not that good in php, i only know how to install it and follow the install steps