centos下，yum安装php5.6

追加CentOS 6.5的epel及remi源。

# rpm -Uvh http://ftp.iij.ad.jp/pub/linux/fedora/epel/6/x86_64/epel-release-6-8.noarch.rpm
# rpm -Uvh http://rpms.famillecollet.com/enterprise/remi-release-6.rpm

以下是CentOS 7.0的源。
# yum install epel-release
# rpm -ivh http://rpms.famillecollet.com/enterprise/remi-release-7.rpm

安装
yum install --enablerepo=remi --enablerepo=remi-php56 php php-opcache php-devel php-mbstring php-mcrypt php-mysqlnd php-phpunit-PHPUnit php-pecl-xdebug php-pecl-xhprof

yum install --enablerepo=remi --enablerepo=remi-php56 php-fpm

其他参考：http://www.centoscn.com/image-text/install/2016/0130/6725.html