The program 'php' can be found in the following packages:
* php7.0-cli
* hhvm
Try: sudo apt install <selected package>

$ whereis php
php: /usr/bin/php.old /usr/bin/php7.0 /usr/lib/php /etc/php /usr/share/php7.0-common /usr/share/php7.0-intl /usr/share/php7.0-json /usr/share/php /usr/share/php7.0-zip /usr/share/php7.0-mcrypt /usr/share/php7.0-mysql /usr/share/php7.0-readline /usr/share/php7.0-opcache /usr/share/php7.0-xml /usr/share/php7.0-mbstring /usr/share/php7.0-gd /usr/share/man/man1/php.1.gz