running "yum update" will update all of your software, including httpd mysql and php, but you could also do "yum update httpd" (and all the others) and it would update just that if there is an update available.
Athlon II X2 240 @2.8 GHz
2 GB G.Skill ddr2 pc2-6400
500 GB Western Digital Caviar Blue HDD
40 GB Western Digital HDD