Thank you for your question.
Please, see below the output
yum repolist
Loaded plugins: priorities
atomic | 1.9 kB 00:00
base | 3.7 kB 00:00
extras | 3.4 kB 00:00
plesk11-base | 1.3 kB 00:00
plesk11-thirdparty | 1.3 kB 00:00
plesk11-updates | 1.3 kB 00:00
updates | 3.4 kB 00:00
198 packages excluded due to repository priority protections
repo id repo name status
atomic CentOS / Red Hat Enterprise Linux 6 - atomicrocketturtle.com 1,025
base CentOS-6 - Base 6,282+99
extras CentOS-6 - Extras 13
plesk11-base Plesk 11.0.9 - Base 113+2
plesk11-thirdparty Plesk 11.0.9 - Thirdparty 2+1
plesk11-updates Plesk 11.0.9 - Updates 0
updates CentOS-6 - Updates 1,434+96
repolist: 8,869
yum list php-opcache
Loaded plugins: priorities
198 packages excluded due to repository priority protections
Error: No matching Packages to list
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That's all...