To install php7.1 you don't need to delete php5. PHP 7.1 will be installed in a separate folder /etc/php/7.1/ First add Dotdeb PPA and import the GPG key of Dotdeb repository apt-get install apt-transport-https lsb-release ca-certificates wget -O /etc/apt/trusted.gpg.d/php.gpg https://packages.sury.org/php/apt.gpg Then add PPA in your server and update echo 'deb https://packages.sury.org/php/ jessie main'...

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