Install yum packages based on regular expression

I would start with:

sudo yum clean all

and then try

sudo yum -y install php-pecl-apc

yum interfaces with the online repository related to your version of CentOS.

rpm is the package manager and packaging format for applications developed for the Red Hat/CentOS platform. Your rpm command is installing a packaged that was downloaded and is not part of a yum repository.

In the Windows world, it's like the difference between Windows Update (yum) and downloading a piece of software and double-clicking an installer (rpm).

It also appears as though you're using a version of postgresql that is newer than the one available through the normal CentOS channels ("Base" and "Updates"). The package being installed by the yum command you listed is coming from a different third-party software repository.

It looks like you're using the postgres database packages provided directly be PostgreSQL instead of the ones that come via CentOS. The instructions and reasoning are detailled here.

As a result, you've been asked to prevent the version that's is distributed with CentOS from installing by using the exclude= statements you listed. This is a precautionary measure to avoid a conflict between the older version of postgresql from CentOS and the newer one you're installing.