How to Connect to MySQL from PHP Applications (Hostname, Port, Credentials)

OpenPanel runs each user service inside its own container. The MySQL/MariaDB container shares its Unix socket with the PHP containers (PHP-FPM and OpenLiteSpeed) of the same user, so PHP applications can connect to the database on localhost just like on a regular server. Other applications (Node.js, Python, Ruby, Java...) run in their own containers and connect through the container hostname instead.

For more information about networks: Network Isolation in OpenPanel

Username/Password: created for the database from OpenPanel UI.

⚠️ Important: Never use 127.0.0.1 as the database host. It connects over TCP inside the PHP container itself, where no database is listening.

Example: WordPress​

When setting up WordPress inside OpenPanel, use the following database configuration in wp-config.php:

define( 'DB_HOST', 'localhost' );

WordPress connects to the database through the Unix socket shared with the PHP container. On older accounts use mysql or mariadb instead.

Example: Custom PHP Application​

In a custom PHP app, you can connect like this:

<?php
$host = "localhost";   // or "mysql" / "mariadb"
$db   = "my_database";
$user = "my_user";
$pass = "my_password";

$dsn = "mysql:host=$host;dbname=$db;charset=utf8mb4";

try {
    $pdo = new PDO($dsn, $user, $pass);
    echo "Connected successfully!";
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}

With localhost, PHP connects through the /var/run/mysqld/mysqld.sock socket, which is set as the default in php.ini (mysqli.default_socket and pdo_mysql.default_socket).

Example: Node.js Application​

For Node.js using mysql2 or sequelize:

const mysql = require('mysql2');

const connection = mysql.createConnection({
  host: 'mysql',       // or "mariadb"
  user: 'my_user',
  password: 'my_password',
  database: 'my_database'
});

connection.connect(err => {
  if (err) {
    console.error('Connection error:', err);
    return;
  }
  console.log('Connected successfully!');
});

Example: Python Application​

Using mysql-connector-python:

import mysql.connector

conn = mysql.connector.connect(
    host="mysql",        # or "mariadb"
    user="my_user",
    password="my_password",
    database="my_database"
)

cursor = conn.cursor()
cursor.execute("SELECT DATABASE();")
print("Connected to:", cursor.fetchone())

✅ Summary:

• PHP apps: use localhost (or mysql / mariadb on older accounts).
• Node.js, Python and other non-PHP apps: use mysql or mariadb on port 3306, they reach the database through the db network.
• Never use 127.0.0.1.