Устранение неполадок php 7 на Ubuntu 14.04

Я использую Ubuntu 14.04, и я пытаюсь установить PHP 7. Я делаю что-то неправильно. Я следовал этим указаниям.

Если я нахожу «php -v» в терминале, он показывает php 7.

Однако, если я смотрю на мой phpinfo (), вывод все еще показывает мой старый php 5.

Теперь, когда я пытаюсь установить что-то, что требует php 7, я получаю следующую ошибку:

    Your requirements could not be resolved to an installable set of packages.

        Problem 1
          - Installation request for alchemy/zippy 0.3.5 -> satisfiable by 
alchemy/zippy[0.3.5].
          - alchemy/zippy 0.3.5 requires ext-mbstring * -> the requested PHP 
extension mbstring is missing from your system.
        Problem 2
          - Installation request for easyrdf/easyrdf 0.9.1 -> satisfiable by 
easyrdf/easyrdf[0.9.1].
          - easyrdf/easyrdf 0.9.1 requires ext-mbstring * -> the requested 
PHP extension mbstring is missing from your system.
        Problem 3
          - Installation request for phpunit/phpunit 4.8.27 -> satisfiable by
 phpunit/phpunit[4.8.27].
          - phpunit/phpunit 4.8.27 requires ext-dom * -> the requested PHP 
extension dom is missing from your system.
        Problem 4
          - alchemy/zippy 0.3.5 requires ext-mbstring * -> the requested PHP 
extension mbstring is missing from your system.
          - drupal/console 0.11.3 requires alchemy/zippy 0.3.5 -> satisfiable
 by alchemy/zippy[0.3.5].
          - Installation request for drupal/console 0.11.3 -> satisfiable by 
drupal/console[0.11.3].

        To enable extensions, verify that they are enabled in those .ini 
files:
          - /etc/php/7.0/cli/php.ini
          - /etc/php/7.0/cli/conf.d/10-mysqlnd.ini
          - /etc/php/7.0/cli/conf.d/10-opcache.ini
          - /etc/php/7.0/cli/conf.d/10-pdo.ini
          - /etc/php/7.0/cli/conf.d/20-calendar.ini
          - /etc/php/7.0/cli/conf.d/20-ctype.ini
          - /etc/php/7.0/cli/conf.d/20-exif.ini
          - /etc/php/7.0/cli/conf.d/20-fileinfo.ini
          - /etc/php/7.0/cli/conf.d/20-ftp.ini
          - /etc/php/7.0/cli/conf.d/20-gd.ini
          - /etc/php/7.0/cli/conf.d/20-gettext.ini
          - /etc/php/7.0/cli/conf.d/20-iconv.ini
          - /etc/php/7.0/cli/conf.d/20-json.ini
          - /etc/php/7.0/cli/conf.d/20-mysqli.ini
          - /etc/php/7.0/cli/conf.d/20-pdo_mysql.ini
          - /etc/php/7.0/cli/conf.d/20-phar.ini
          - /etc/php/7.0/cli/conf.d/20-posix.ini
          - /etc/php/7.0/cli/conf.d/20-readline.ini
          - /etc/php/7.0/cli/conf.d/20-shmop.ini
          - /etc/php/7.0/cli/conf.d/20-sockets.ini
          - /etc/php/7.0/cli/conf.d/20-sysvmsg.ini
          - /etc/php/7.0/cli/conf.d/20-sysvsem.ini
          - /etc/php/7.0/cli/conf.d/20-sysvshm.ini
          - /etc/php/7.0/cli/conf.d/20-tokenizer.ini
        You can also run `php --ini` inside terminal to see which files are
 used by PHP in CLI mode.

Кто-нибудь знает, что мне нужно исправить, чтобы запустить php 7 в моей системе? [ ! d5]