A server side user can have special permissions to won you WordPress application.
If you have set one up and it stops working after you upgrade your PHP it is likely related to SSH2 PHP module.
A while back I took advantage of this post from Digital Ocean about Secure Updates and Installations in WordPress on Ubuntu and it worked great until I upgraded to PHP7.
I had upgraded from PHP 5 to PHP 7. After upgrading to PHP 7 it is necessary to install PHP 7’s version of the ssh2 package.
How to install ssh2 for php7 on ubuntu
It’s pretty easy, really.
ssh into your server via the command line.
Then update you package manager for Ubuntu.
⨊ $>sudo apt-get install
Then install the PHP 7 ssh2 package with the following command.
⨊ $>sudo apt-get install php7.1-ssh2
HINT: If your PHP version is 7.0 then use php7.0-ssh2 instead.
Then restart your apache2 server
⨊ $>sudo service apache2 restart
Hope this helps someone!