直接命令升级
add-apt-repository ppa:ondrej/php
$ apt-get update
$ apt-get upgrade php
升级后安装对应的扩展
apt-get install php-mbstring
apt-get install php-gd
apt-get install php-dom
apt-get install php-mysql
apt-get install php-curl
如果上面安装有问题可以
apt-get install php7.2-curl
...
/usr/bin/php -v
PHP 7.2.4-1+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Apr 5 2018 08:53:57) ( NTS )
参考地址：https://laravel-china.org/articles/6845/ubuntu-php70-upgrade-to-71
