no upset mike,,
if you really need to run php5.3 there is not available from standard repository
what you have to do is install another repository
for your info rpmforge repo dont have that file
i suggest u use remi repo its easy,
have a visit to http://rpms.famillecollet.com/
download install to suite your system
then uses yum command with --enablerepo=remi, as said by novice06 please test at staging environment.