Docker-Compose Using PHP (MySQLi) to Connect to MySQL database - php

Question

Ok, so here's the deal: I'm using Docker-Compose to create 3 services: one for the platform, one for db (mysql) and the third for PHPMyAdmin
I'm trying to use mysqli to connect to the database on port 5001.
What’s interesting is that I can connect to the database using SQL Workbench and PHPMyAdmin with the same parameters, but I get an error (seen below) when connecting using PHP MySQLi
Platform:
$db = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME, DB_PORT);
The host is 127.0.0.1, the DB_USER is root with its respective password, I've provided a DB_Name and the port is 5001.
My Docker-Compose.yml looks like this:
version: '3.3'
services:
platform:
build: .
ports:
- "5000:80"
links:
- db:mysql
db:
image: mysql:5.7
volumes:
- db_data:/var/lib/mysql
restart: always
ports:
#- "5001:80"
- "5001:3306"
environment:
MYSQL_ROOT_PASSWORD: some_great_password_here
MYSQL_DATABASE: DB_NAME_HERE
MYSQL_USER: USERNAME
MYSQL_PASSWORD: PASSWORD
phpmyadmin:
image: phpmyadmin/phpmyadmin
links:
- db:mysql
ports:
- 8181:80
environment:
MYSQL_USERNAME: USERNAME
MYSQL_ROOT_PASSWORD: PASSWORD
volumes:
db_data:
For some reason, I keep getting the error:
mysqli::mysqli(): (HY000/2003): Can't connect to MySQL server on '127.0.0.1' (111) in ...
Any tips or a solution would be much appreciated!

Answer 1

I found a solution to my problem after churning through documentation and other Stackoverflow posts.
When attempting to connect to the database from inside a container, we need to use the container / service name as opposed to 'localhost' or 127.0.0.1. This is because when we call "localhost," it's looking for localhost inside each container. We need to connect to a MySQL database inside a different container, via a network bridge.
The way we do this is to simply alias the container name as the host, such that:
$db = new mysqli("db", DB_USER, DB_PASS, DB_NAME, DB_PORT);
Notice that the Hostname is the container name "db," as defined in the docker-compose.yml file. This works because of the docker network bridge that is created between containers. The port is the default MySQL port of 3306.
It's important to note however, if we want to use an "external" app like Sequel Pro or Workbench to connect to the database, we can use localhost or 127.0.0.1 to connect to the database since we are not dealing directly with containers. It should be noted however, that the default port of 3306 won't work in this situation. We need to map an external port with 3306. In my case, that would be 5001, as shown in my docker-compose.yml file.

Answer 2

You have mapped mysql port to 3306 as per
- "5001:3306"
You should try to connect at port 3306 instead of 5001. Make sure that your containers are using Bridge Networking for them to communicate with each other.
$db = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME, 3306);