start following wordpress.yml with

sloppy start -var=URI:mywordpress.sloppy.zone -var=DBUSER:wpadmin -var=DBPASS:secret -var=DBROOT:moresecret wordpress.yml

wordpress.yml:

version: "v1"
project: "wordpress"
services:
  frontend:
    apache:
      image: "wordpress:4.6.0"
      instances: 1
      mem: 512
      domain: "$URI"
      port: 80
      env:
        - WORDPRESS_DB_HOST: "mysql.backend.wordpress"
        - WORDPRESS_DB_USER: "$DBUSER"
        - WORDPRESS_DB_PASSWORD: "$DBPASS"
      volumes:
        - path: "/var/www/html"
          size: "8GB"
      dependencies:
        - "../backend/mysql"
  backend:
    mysql:
      image: "mysql"
      instances: 1
      mem: 512
      port: 3306
      env:
        - MYSQL_ROOT_PASSWORD: "$DBROOT"
        - MYSQL_USER: "$DBUSER"
        - MYSQL_PASSWORD: "$DBPASS"
        - MYSQL_DATABASE: "wordpress"
      healthchecks:
        - type: "TCP"
          timeout: 20
          interval: 10
          max_consecutive_failures: 4
          grace_period_seconds: 300
      volumes:
        - path: "/var/lib/mysql"
          size: "8GB"


Then edit the yml and add phpmyadmin:

version: "v1"
project: "wordpress"
services:
  frontend:
    apache:
      image: "wordpress:4.6.0"
      instances: 1
      mem: 512
      domain: "$URI"
      port: 80
      env:
        - WORDPRESS_DB_HOST: "mysql.backend.wordpress"
        - WORDPRESS_DB_USER: "$DBUSER"
        - WORDPRESS_DB_PASSWORD: "$DBPASS"
      volumes:
        - path: "/var/www/html"
          size: "8GB"
      dependencies:
        - "../backend/mysql"
  backend:
    mysql:
      image: "mysql"
      instances: 1
      mem: 512
      port: 3306
      env:
        - MYSQL_ROOT_PASSWORD: "$DBROOT"
        - MYSQL_USER: "$DBUSER"
        - MYSQL_PASSWORD: "$DBPASS"
        - MYSQL_DATABASE: "wordpress"
      healthchecks:
        - type: "TCP"
          timeout: 20
          interval: 10
          max_consecutive_failures: 4
          grace_period_seconds: 300
      volumes:
        - path: "/var/lib/mysql"
          size: "8GB"
    phpmyadmin:
      image: "phpmyadmin/phpmyadmin"
      domain: "padmin.sloppy.zone"
      instances: 1
      mem: 512
      port: 80
      env:
        - PMA_HOST: "mysql.backend.wordpress"
      volumes:
        - path: "/sessions"



Then use "sloppy change" to update the project:

sloppy change -var=URI:mywordpress.sloppy.zone -var=DBUSER:wpadmin -var=DBPASS:secret -var=DBROOT:moresecret wordpress-phpmyadmin.yml