默认CentOs 的源 并没有php7的安装路径，所以需要手动添加源：
# rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
# rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm
然后安装成功以后，开始php7以及相应依赖和扩展的安装：
yum install php71w php71w-bcmath php71w-cli php71w-common php71w-dba php71w-devel php71w-embedded php71w-enchant php71w-fpm php71w-gd php71w-imap php71w-intl php71w-ldap php71w-mbstring php71w-mysqlnd php71w-odbc php71w-opcache php71w-pdo php71w-pear php71w-pecl-apcu php71w-pecl-imagick php71w-pecl-xdebug php71w-pgsql php71w-phpdbg php71w-process php71w-pspell php71w-recode php71w-snmp php71w-soap php71w-tidy php71w-xml php71w-xmlrpc
安装成功!