fixed env format and added phpmyadmin doc

docker-compose.yml

@@ -22,10 +22,10 @@ services:
   mariadb:
     image: mariadb:latest
     environment:
-      MYSQL_ROOT_PASSWORD: rootpassword
-      MYSQL_DATABASE: dbname
-      MYSQL_USER: user
-      MYSQL_PASSWORD: password
+      - MYSQL_ROOT_PASSWORD=rootpassword
+      - MYSQL_DATABASE=dbname
+      - MYSQL_USER=user
+      - MYSQL_PASSWORD=password
     volumes:
       - ./data/db:/var/lib/mysql
     networks:

docs/phpmyadmin.md

@@ -0,0 +1,5 @@
+# PHPMYADMIN
+
+You may want to use PHPmyAdmin for testing.
+
+Checkout [Docker Cookbooks](https://github.com/nickyeoman/docker-compose-cookbooks/blob/master/phpmyadmin/docker-compose.yml) for an example.