At first you need to install composer, you can use my script with the command :
bash <(wget --no-check-certificate -O - https://git.virtubox.net/virtubox/debian-config/raw/master/composer.sh)
Then login as www-data :
su - www-data
If you can’t login as www-data, you will have to edit the file /etc/passwd
and to replace /usr/sbin/nologin
by /bin/bash
on the line :
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
Then you should be able to login as www-data.
Go into the phpmyadmin folder :
cd 22222/htdocs/db/pma
and use the command :
composer update