老师为啥我按照你的步骤，到sudo apt-get -y install php7.1
显示
root@iZwz99qnmldt4n744noo9gZ:~# sudo apt-get -y install php7.1
sudo: unable to resolve host iZwz99qnmldt4n744noo9gZ
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package php7.1
E: Couldn't find any package by regex 'php7.1'
这个