Docker-Compose Cannot Connect to Server w/ mysqli_connect - php

Question

I have recently installed docker-compose on Ubuntu. I can connect to my local host, phpmyadmin and stuff. However, when I try to connect to it with mysqli_connect, I can reach the server but I cannot access it with Warning: mysqli_connect(): (HY000/2002).
Here is the php code I am using to try to connect:
// username and password belong to the phpmyadmin, before that I tried docker for both username and pwd.
Edit: staj is the name of database i created in phpmyadmin.
<?php
$dbHost="127.0.0.1";
$dbUser="root";
$dbPass="root";
$dbName="staj";
$conn=mysqli_connect($dbHost, $dbUser, $dbPass, $dbName);
if ($conn){
}else{
die("Connection Failed!");
}
?>
And here is my docker-compose.yml:
version: "3"
services:
webserver:
build:
context: ./bin/${PHPVERSION}
container_name: '${COMPOSE_PROJECT_NAME}-${PHPVERSION}'
restart: 'always'
ports:
- "${HOST_MACHINE_UNSECURE_HOST_PORT}:80"
- "${HOST_MACHINE_SECURE_HOST_PORT}:443"
links:
- database
volumes:
- ${DOCUMENT_ROOT-./www}:/var/www/html
- ${PHP_INI-./config/php/php.ini}:/usr/local/etc/php/php.ini
- ${VHOSTS_DIR-./config/vhosts}:/etc/apache2/sites-enabled
- ${LOG_DIR-./logs/apache2}:/var/log/apache2
environment:
APACHE_DOCUMENT_ROOT: ${APACHE_DOCUMENT_ROOT-/var/www/html}
PMA_PORT: ${HOST_MACHINE_PMA_PORT}
MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
database:
build:
context: "./bin/${DATABASE}"
container_name: '${COMPOSE_PROJECT_NAME}-${DATABASE}'
restart: 'always'
ports:
- "127.0.0.1:${HOST_MACHINE_MYSQL_PORT}:3306"
volumes:
- ${MYSQL_INITDB_DIR-./config/initdb}:/docker-entrypoint-initdb.d
- ${MYSQL_DATA_DIR-./data/mysql}:/var/lib/mysql
- ${MYSQL_LOG_DIR-./logs/mysql}:/var/log/mysql
environment:
MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
MYSQL_DATABASE: ${MYSQL_DATABASE}
MYSQL_USER: ${MYSQL_USER}
phpmyadmin:
image: phpmyadmin/phpmyadmin
container_name: '${COMPOSE_PROJECT_NAME}-phpmyadmin'
links:
- database
environment:
PMA_HOST: database
PMA_PORT: 3306
PMA_USER: root
PMA_PASSWORD: ${MYSQL_ROOT_PASSWORD}
MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
MYSQL_USER: ${MYSQL_USER}
MYSQL_PASSWORD: ${MYSQL_PASSWORD}
UPLOAD_LIMIT: ${UPLOAD_LIMIT}
MEMORY_LIMIT: ${MEMORY_LIMIT}
ports:
- '${HOST_MACHINE_PMA_PORT}:80'
volumes:
- /sessions
- ${PHP_INI-./config/php/php.ini}:/usr/local/etc/php/conf.d/php-phpmyadmin.ini
redis:
container_name: '${COMPOSE_PROJECT_NAME}-redis'
image: redis:latest
ports:
- "127.0.0.1:${HOST_MACHINE_REDIS_PORT}:6379"

Answer 1

Solution:
$dbHost="database";
$dbUser="docker";
$dbPass="docker";
$dbName="docker";
It turns out that docker for username and pwd was correct but the host name was incorrect.
I got that "docker" from the .env.

Answer 2

Seems you've already found the way to connect, but here's why it works that way:
You're using distinct docker containers for each service, which is correct, but that means your application isn't trying to connect locally (127.0.0.1) because the database isn't running on the same container.
Docker Compose networking allows hosts defined in the same docker-compose file to communicate with each other by using the host names which are defined as the service name (the next level under service), so in your case you have hosts webserver, database, phpmyadmin, and redis.
Simply updating the host name you're trying to connect to from 127.0.0.1 to database should be all you need to do.