found out problem comes from the new PHP version (5.4, 5.4), which installed in a separate repo.
So, we just need to install php-bcmath in the main repo (version 5.3) using command:
yum install php-bcmath --enablerepo=remi
With "remi" is the main repo, you can see it by go to /etc/yum.repos.d then using ll
You can try (for Centos 6.4)
rpm -Uvh yum install php54w
yum install yum-plugin-replace
yum replace php-common --replace-with=php54w-common
yum install php54w-bcmath
But it may cause another problem about versions.
The simple way is uninstall php 5.4 (or 5.5),
install php 5.3, install php-bcmatch then update to php5.4 (or newer)