An "issue" after ppa:ondrej/php5 deprecation - php

Question

Today I was upgrading PHP 5.5 on my LEMP stack to version 5.5.35. After upgrading I received an on-screen message that the repo ppa:ondrej/php5 is deprecated and if I want to continue receiving php updates I should move onto ppa:ondrej/php which now includes PHP 5.5, PHP 5.6 and PHP 7.0 in one place. Previously these versions were in different repos.
I followed Ondřej's advice and I run:
sudo add-apt-repository ppa:ondrej/php
And then:
sudo apt-get update
sudo apt-get upgrade --show-upgraded
All went fine, except that two packages were held back: php-pear and pkg-php-tools. That of course happens from time to time when package dependencies change so I run:
sudo apt-get install php-pear pkg-php-tools
Then, I got a message that additionaly the following packages will be installed:
php-cli php-common php-xml php7.0-cli php7.0-common php7.0-json php7.0-opcache php7.0-readline php7.0-xml
Immediately I felt that something is wrong here. Why the hell I need PHP 7.0 packages when I'm running PHP 5.5? However I went with option YES and apparently everything went fine. The server is running, no errors or confilcts that I'm aware of. Then I was curious and I checked what version of PHP am I running?
php -v
The output was:
PHP 7.0.6-1+donate.sury.org~trusty...
What the hell happened here? How did I ended up installing PHP 7.0 and why the server/site isn't crashing? Since I use nginx with php-fpm, by examining the nginx.conf I can clearly see that nginx is pointing to php5-fpm.sock so I definitely run php5-fpm here. Plus the site is up, and there are no PHP errors in the log.
I also went and I've uploaded a phpinfo file. The file shows I'm using PHP 5.5.35. So there are two conflicting messages where command via ssh shows that the PHP version is 7.0.6, while the phpinfo file shows that the server is using PHP 5.5.35.
So I run:
sudo apt-get remove php7.0-common
All previously added php7.0 packages were removed and also those two that were initially being held back.
Now, after checking the PHP version via SSH it showed correctly 5.5.35. While all this was happening the server had no trouble whatsoever. The status at this moment is that I don't have php-pear and pkg-php-tools packages, but if I try to install them all those php7.0 packages will have to be installed too.
I've also examined /etc/php5 and /etc/php folders. In this second folder there is 7.0 folder where cli and mods-available folders with mods inside reside.
Can someone explain to me what is happening here and what should I do? Are php5 and php7.0 simultaneously running on the server? Do I need those two packages that were held back in LEMP + Wordpress stack?

Answer 1

php-pear and pkg-php-tools must depend on PHP CLI for default PHP version and that's PHP 7.0. Installing php-cli pulls php7.0-cli that will install /usr/bin/php7.0 and registers it as alternative with highest (70) priority to provide /usr/bin/php.
Installing PHP CLI binary is mostly harmless unless you need to run PHP scripts locally using command line. I could recommend two approaches:
Rewriting those scripts to specify required version, e.g. changing php <script> to php5.6 <script>, or
Use update-alternatives to switch /usr/bin/php to your desired PHP version: a) switch to specific version update-alternatives --set php /usr/bin/php5.6 or b) update-alternatives --config php configure the version by hand
More thorough version of the migration guide is located in DEB.SURY.ORG Wiki.
To use the new PHP FPM packages, you need to install:
sudo apt-get install php5.5-fpm # for PHP 5.5
sudo apt-get install php5.6-fpm # for PHP 5.6
sudo apt-get install php7.0-fpm # for PHP 7.0
and adjust the socket accordingly, look into default FPM configuration:
sudo editor /etc/php/X.Y/fpm/pool.d/www.conf
for the socket location (it's /run/php/phpX.Y-fpm.sock by default).