网上很多方案，使用yum安装一般采用下面的方法（此种方法有可能会安装不成功）；
安装epel-release
rpm -ivh http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm
(由于网站原因、防火墙、iptables受限等原因，会报 curl: (7) Failed connect to dl.fedoraproject.org:80; 拒绝连接 的错误)
2.安装PHP7的rpm源
rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm
3.安装PHP7
yum
install
php70w
建议使用下面方案安装，本人亲测可用：
1.安装epel-release
yum -y install epel-release
2.获取PHP7的yum源
rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm
3.安装PHP7
yum install php70w
4.验证安装
php -v