Access denied when making connection from php container to mysql container

Question

I’ve been searching the web for hours but do not find any solution to my problem. I have 3 containers: - nginx - php - mysql

They are all connected to the same network.

If I try to log into mysql from the mysql container, all works fine. If I try to make a pdo connection from the php container to the mysql container, I always receive the message “Access denied for user”. I have no idea why. Let me show you guys what happens.

This is my docker-compose file:

version: ‘3’

networks:
danvers:

services:
#WebServer Service
danvers-nginx:
image: nginx:stable
container_name: danvers-nginx
ports:
- ‘8080:80’
volumes:
- ./:/var/www
- ./docker/nginx/default.conf:/etc/nginx/conf.d/default.conf
depends_on:
- danvers-php
- danvers-mysql-app
networks:
danvers:

#PHP Service
danvers-php:
build:
context: ./
dockerfile: Dockerfile
container_name: danvers-php
volumes:
- ./:/var/www
- ./docker/php/local.ini:/usr/local/etc/php/conf.d/local.ini
depends_on:
- danvers-mysql-app
networks:
danvers:

#MySQL Service for App Database
danvers-mysql-app:
image: mysql:5.7.22
container_name: danvers-mysql-app
restart: unless-stopped
tty: true
ports:
- “33061:3306”
environment:
- MYSQL_ROOT_PASSWORD=securerootpassword
- MYSQL_DATABASE={DB_APP_DATABASE} 
- MYSQL_USER={DB_APP_USERNAME}
- MYSQL_PASSWORD=${DB_APP_PASSWORD}
volumes:
- danvers-app-data:/var/lib/mysql
- ./docker/mysql/my.cnf:/etc/mysql/my.cnf
networks:
danvers:

volumes:
danvers-app-data:

If I go inside the danvers-php container and open a interactive shell for php and try to make a pdo connection I get this:

php > new PDO(‘mysql:host=danvers-mysql-app;dbname=danvers-app’, ‘d-app-conn-user’, ‘cable’);

Warning: Uncaught PDOException: SQLSTATE[HY000] [1045] Access denied for user ‘d-app-conn-user’@‘danvers-php.projectdanvers_danvers’ (using password: YES) in php shell code:1

Stack trace:
#0 php shell code(1): PDO->__construct(‘mysql:host=danv…’, ‘d-app-conn-user’, ‘cable’)
#1 {main}
thrown in php shell code on line 1

The connection is made as I see the incoming request in the log from danvers-mysql-app. What seems odd here is that the user-format in the error looks strange. I have no clue where the “danvers-php.projectdanvers_danvers” comes from. This is a concatenation of the php container and the network the containers are on. I think this is why the access is denied by have no clue how to change this as I assumed this should be the mysql containers name instead.

Does anybody have a clue to what I am doing wrong here?

Thanks for any reply or feedback.

EDIT:
In my mysql container I logged in with root and get this users list:

+-----------------+-----------+
| user | host |
+-----------------+-----------+
| d-app-conn-user | % |
| root | % |
| mysql.session | localhost |
| mysql.sys | localhost |
| root | localhost |
+-----------------+-----------+

Output from select user, host from mysql.user

The % for host name means no matter what the hostname is, as long as the username is correct, I should be able to login. The credentials are working from inside the mysql container but when the connection is made from another container, it fails. If I try to make a connection with SequelPro from my local machine through port 33061, it also works. The problem only exist when it's an inter container connection.

EDIT2:
So I changed the nginx and php configuration with a php:7.4-apache configuration in my Dockerfile and now this problem does not exist anymore. I am able to log into the mysql container from the php container. The problem is related to the Nginx web server.