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PHP can't find MySQL server in Docker

So I have a set of Docker services (running on Ubuntu) that are almost working at the moment:

I have them set up in the docker-compose defined below, and the PHPMyAdmin is able to interface with the SQL server, but using the PHP connection script below, and calling db_connect(), gives the following error page:

db_connect()

Warning: mysqli::__construct():(HY000/2002): No such file or directory in /var/www/html/api/sql_db.php on line 12
MySQLi Connection failed: No such file or directory
SESSION: Array ( [sql_server] => db [username] => root[password] => test [dbname] => bravo


File containing db_connect():

db_connect()

<?php
session_start();
$servername = "db";
$username = "root";
$password = "test";
$dbname = "bravo";
$_SESSION['sql_server'] = $servername;
$_SESSION['username'] = $username;
$_SESSION['password'] = $password;
$_SESSION['dbname'] = $dbname;
function db_connect()
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_errno)
printf("MySQLi Connection failed: %sn", $conn->connect_error."<br>SESSION: ");
print_r($_SESSION);
session_destroy();
unset($_SESSION);
exit();




docker-compose.yml:

docker-compose.yml

version: '3'

services:
db:
image: mysql:5.7.23
container_name: db
command: --default-authentication-plugin=mysql_native_password
ports:
- 3306:3306
environment:
MYSQL_DATABASE: bravo
MYSQL_USER: user
MYSQL_PASSWORD: test
MYSQL_ROOT_PASSWORD: test
restart: always
volumes:
- ./dump:/docker-entrypoint-initdb.d
- ./db/data/mysql:/var/lib/mysql
networks:
- default

phpmyadmin:
image: phpmyadmin/phpmyadmin
links:
- db
ports:
- 8000:80
environment:
MYSQL_USER: user
MYSQL_PASSWORD: test
MYSQL_ROOT_PASSWORD: test
depends_on:
- db

websrv:
build: .
ports:
- 8080:80
volumes:
- ./www:/var/www/html
links:
- db
networks:
- default
depends_on:
- db


and finally, the Dockerfile referenced by the docker-compose for the websrv service:

Dockerfile

docker-compose

websrv

FROM php:7.1.2-apache

RUN docker-php-ext-install mysqli


I've gone through a number of forum posts on why mysqli wouldn't connect, but I haven't found an answer that solves my problem yet.

I've tried getting the internal ip of the docker container as well, but I haven't had any luck.

My choice of the docker images was a result of me trying to simply get php & mysqli, phpMyAdmin, and MySQL all working together. Any functioning combination of the three would be great for me, but surprisingly I haven't really found any public repo that's done it yet.

Thanks for any pointers.

docker-compose up

db

localhost

db

3 Answers
3

In the docker compose, the link alias is "service: alias"(https://docs.docker.com/compose/compose-file/compose-file-v2/#links).
I think in your example, in the webserver, the hostname of database is 'mysql'.

ping db

ping mysql

links: - db

I dont know if it could be use full but my connectDB file is:

<?php
$conn = mysqli_connect("localhost","root","password","nameDb");
// Check connection
if (mysqli_connect_errno())

echo "Failed to connect to MySQL: " . mysqli_connect_error();

?>


I found my problem: I did a PHP goof.
The way that I had my file written, the variables were defined outside of the function, and when the scope changed to inside the function, those values were all either undefined or null.

The fix for this admittedly stupid problem is to put those value definitions inside the function, like so.

<?php
function db_connect()
$servername = "db";
$username = "root";
$password = "test";
$dbname = "bravo";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_errno)
printf("MySQLi Connection failed: %sn", $conn->connect_error."<br>SESSION: ");
print_r($_SESSION);
session_destroy();
unset($_SESSION);
exit();

return $conn;



Then, the connection can be made by calling $conn = db_connect(); after the file this exists in has been imported.

$conn = db_connect();

Thanks all for your efforts.

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