Не удалось найти ни одного пакета с помощью регулярного выражения ‘php5.6’

Я пытаюсь перейти с PHP 5.5.38 на PHP 5.6. Я следую инструкциям доступно на SO, но я получаю следующие сообщения об ошибках:

sudo apt-get -y install php5.6 php5.6-mcrypt php5.6-mbstring php5.6-curl php5.6-cli php5.6-mysql php5.6-gd php5.6-intl php5.6-xsl
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package php5.6
E: Couldn't find any package by regex 'php5.6'
E: Unable to locate package php5.6-mcrypt
E: Couldn't find any package by regex 'php5.6-mcrypt'
E: Unable to locate package php5.6-mbstring
E: Couldn't find any package by regex 'php5.6-mbstring'
E: Unable to locate package php5.6-curl
E: Couldn't find any package by regex 'php5.6-curl'
E: Unable to locate package php5.6-cli
E: Couldn't find any package by regex 'php5.6-cli'
E: Unable to locate package php5.6-mysql
E: Couldn't find any package by regex 'php5.6-mysql'
E: Unable to locate package php5.6-gd
E: Couldn't find any package by regex 'php5.6-gd'
E: Unable to locate package php5.6-intl
E: Couldn't find any package by regex 'php5.6-intl'
E: Unable to locate package php5.6-xsl
E: Couldn't find any package by regex 'php5.6-xsl'

Кто-нибудь знает, что вызывает эту проблему?

Постскриптум: Я нахожусь на Debian GNU / Linux 7 (wheezy)