我刚刚访问了这个网站：https://community.linuxmint.com/tutorial/view/486并尝试按照如何安装薄荷的教程。 appache安装工作正常。但是，当我粘贴以下代码来安装php时，它不起作用
sudo apt-get install php5 libapache2-mod-php5
这是我输入命令后显示的内容：
sidney-the-programmer sidney # sudo apt-get install php5 libapache2-mod-php5
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libapache2-mod-php5 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
Package php5 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'php5' has no installation candidate
E: Package 'libapache2-mod-php5' has no installation candidate
还有另一个吗？我身边有什么问题吗？