Cannot install PHP about killersoft-yum HOT 2 OPEN

Red Hat Enterprise Linux Server release 5.3 (Tikanga)

[root@host51 itchy]# yum update 'php*'
Loaded plugins: excludes, fastestmirror, fedorakmod, noelver, noproxy, 
priorities,
repovars, rhnplugin, security
This system is not registered with RHN.
RHN support will be disabled.
Loading mirror speeds from cached hostfile
...snip...
--> Finished Dependency Resolution
php-pdo-5.1.6-23.2.el5_3.i386 from installed has depsolving problems
  --> Missing Dependency: php-common = 5.1.6-23.2.el5_3 is needed by package
php-pdo-5.1.6-23.2.el5_3.i386 (installed)
Error: Missing Dependency: php-common = 5.1.6-23.2.el5_3 is needed by package
php-pdo-5.1.6-23.2.el5_3.i386 (installed)

Hi guys,

I apologize for the delay getting back to you. I suggest two things to 
troubleshoot this:

1. Try setting priority=1 on the [killersoft] repo in 
/etc/yum.repos.d/killersoft.repo

2. If the above doesn't work, uninstall your existing PHP first with a 'yum 
remove php-
common', then do 'yum install php --disablerepo=base'