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 라는 오류가 뜬다?
sudo aptitude purge `dpkg -l | grep php| awk '{print $2}' |tr "\n" " "`sudo add-apt-repository ppa:ondrej/phpsudo apt-get update
sudo apt-get install php7.0위와같이 입력하면 된다.