我想在Ubuntu中安装php7或7.1，但我不能
我试着用这个代码：

sudo add-apt-repository ppa:ondrej/php
 sudo apt-get update
 sudo apt-get install -y php7.1

这就是结果

sudo: unable to resolve host myvps
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'

PHP 7.0

Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package php7.0
E: Couldn't find any package by regex 'php7.0'

但是我知道我可以安装php5，但是我不想！此命令的se结果php -v

root@myvps:~# php -v
The program 'php' is currently not installed. You can install it by typing:
apt-get install php5-cli

以下是我的Ubuntu信息：

root@myvps:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 15.04
Release:        15.04
Codename:       vivid

怎么了？有可能解决这个问题吗？