Role of Docker, nginx, PHP, MySQL | Introduction to WordPress server for hosts

When you run WordPress on a VPS, you will come across the names Docker, nginx, PHP, and MySQL.Although they are all sometimes referred to as “servers,” their roles are different.

The host does not need to remember any commands. However, if you know which parts do what, it will be easier to explain when a failure occurs, such as “the entire site has stopped”, “only images are visible”, or “a database connection error has occurred”.

First, let’s look at the big picture.

Guest’s browser → nginx → Run WordPress with PHP → Get articles and settings from MySQL → Return HTML to browser

In a configuration that uses Docker, each component is operated separately and managed in summary.

Comparing it to an inn

Technology	Inn analogy	Main roles
Docker	Business divisions and management ledger for each person in charge	Run software reproducibly in an isolated environment
nginx	Entrance/Front desk	URL reception, sorting, image distribution, HTTPS
PHP	Responsible for assembling guidance	Creating pages by running WordPress programs
WordPress	Accommodation information business	Deciding on content using articles, themes, and plugins
MySQL	Accommodation book/reference archive	Save and search articles, settings, users, etc.

Analogies are the gateway to understanding. The actual configuration may use other parts such as Apache, MariaDB, CDN, cache, etc.

Until the page is displayed

When a guest opens the guest room page, the general flow is as follows.

Browser accesses the domain URL
DNS indicates the server to connect to
nginx accepts HTTPS connections
Return images etc. directly or pass WordPress processing to PHP
PHP runs WordPress
WordPress queries MySQL for articles and settings
PHP assembles HTML
nginx returns results to browser
Browser displays page

Multiple parts move behind one screen, so even if WordPress is up to date, it will not be displayed if there is a problem with the OS, PHP, or database.

Role of Docker

Docker official documentation describes a container as a process that runs in isolation on a host. I have a configuration where WordPress, nginx, PHP, and the database are separated into separate containers.

What you can get with Docker

Software and necessary files can be handled as a unit.
Easily reduces configuration differences between development, testing, and production
Easy to start, stop, and update each part
Record configuration to file for easy reproduction

What Docker doesn’t do automatically

Updates to the OS and Docker itself
Safe image selection and update
Password/confidential information protection
Database backup
Disk space and log management
Fault monitoring
Reservation confirmation after WordPress update

Even if you delete the container and recreate it, you may lose articles and images if you save the data in the wrong location. Having Docker does not eliminate the need for backups.

Role of nginx

nginx official beginner’s guide explains how to distribute static files, proxies, routing to PHP via FastCGI, etc.

The main tasks in WordPress configuration are:

Receive HTTP/HTTPS access
Select target sites by domain
Returns images, CSS, JavaScript, etc.
Pass access processed by PHP to PHP-FPM
Set limits such as size and time
Encrypt communication using TLS certificate
Record access error log

Example when there is a problem with nginx

Unable to connect to entire site
Errors such as 502 and 504
HTTPS warning or another site is displayed
Unable to upload large images
Only specific URLs become 404
Repeated redirects

Check the grammar and back up before changing settings, and check all domains after updating.

Role of PHP

PHP Official Manual explains that PHP is a language that is executed on the server side and sends the generated HTML to the browser. WordPress itself and many themes and plugins run on PHP.

Examples where PHP is responsible are as follows.

WordPress processing according to URL
Get articles and settings from MySQL
Generate HTML using themes
Processing form input
Execute plugin functions
Calling the email sending process

Example when there is a problem with PHP

“Serious error” is displayed
White screen appears
502 error occurs
Only the management screen does not work
Only specific plugin functions fail
Memory shortage or processing time exceeds

If you update PHP, old themes and plugins may not be compatible. Don’t update WordPress and PHP changes at the same time, check them in a test environment first.

Role of WordPress

WordPress is a web application that runs on PHP.

Manage articles and fixed pages
Decide the look with the theme
Add SEO, forms, reservations, and more with plugins
Manage administrator and editor permissions
Save content to MySQL

Even when considering just WordPress backups, you need both files and databases. For more information, see Backup and restore before WordPress update.

Role of MySQL

MySQL official documentation describes MySQL as an SQL database server that supports multiple users.

WordPress primarily stores the following:

Articles, static pages, drafts, revision history
Users and permissions
Site URL and various settings
Comment
Menus and widgets
Tables and settings created by the plugin

The actual image is usually saved as a file, and the image title, URL, etc. are also saved in the database. Therefore, inconsistencies occur when the files and databases do not match in time.

Example when there is a problem with MySQL

“Error establishing database connection”
Unable to save articles and settings
Page display is extremely slow
Unable to write due to insufficient disk
Repeatedly restarting only the database

Rather than exposing MySQL directly to the Internet, we configure it so that it can be used only from necessary connection sources such as WordPress.

Container and data storage location

One of the most important aspects of Docker configuration is the distinction between containers and persistent data.

Container: Re-createable execution environment
Image: Designer who creates containers
Volume mount: Data to be saved such as article images and DB
Configuration file for Compose etc.: Which parts are connected and how?

Designs that place data only within the container may lose it when recreated. Allow administrators to explain where current WordPress images, MySQL data, settings, and certificates are stored.

Updates are separated into layers

If you update everything at once, you will not be able to identify the cause.

Record current configuration and version
Back up files, DB, and configuration files
Update one layer in test environment
Check the log and startup status
Check the WordPress display and management screen
Check reservation/form/email
Update only one layer during production
Check the same

Summary of major updates for OS, Docker, nginx, PHP, MySQL, and WordPress on the same day.

Order of viewing in case of failure

the host logs symptoms, not commands.

Symptoms	Candidates for layers to check
Unable to connect to entire domain	DNS, VPS, network, nginx
Only images are visible, but no text	PHP, WordPress, MySQL
502 error	Connection from nginx to PHP, etc.
DB connection error	MySQL, credentials, capacity, network
Serious error only on the admin screen	PHP, themes, plugins
Only inquiries not received	WordPress, PHP, email route
Do not open only the reservation link	WordPress content, external reservation service

It records the URL, time of occurrence, screen, last change, and whether it happens to everyone. Do not include confidential information or customer data in screenshots.

Minimal monitoring

VPS is running
HTTPS connection to nginx possible
PHP responds
Necessary connection to MySQL possible
There is enough disk space
TLS certificate expired
Backup is successful
Top and reservation line are normal
You will receive an inquiry email

Even if the container is “starting”, it does not necessarily mean that the app will work correctly. Also check the actual page from the outside.

Questions to ask the administrator

Are you using Docker? Where is the configuration file?
Who is in charge of current versions and updates of nginx, PHP, and MySQL?
Where are WordPress images and DB permanently saved?
Where to safely manage confidential information
Who checks logs and disk space?
Does the backup include configuration files, images, DB?
Will I be notified if one container stops?
How to hand over configuration and data at the end of the contract

No secret value is required for the answer. Only record the location, method, and person in charge.

Prompt for AI to explain configuration

Please explain the inn's WordPress server configuration for IT beginners.
Do not connect, update, restart, or change settings yet.

Please organize the following from the readable configuration materials.
- Flow of guest access to page display
- Role of Docker, nginx, PHP, WordPress, MySQL
- Types of storage locations for persistent data and settings for each part
- Symptoms visible when each part stops
- Person responsible for updates, monitoring, and backups
- Questions to ask the management company

Do not display passwords, private keys, environment variable values, or customer information.
Do not write speculation as fact; instead, mark it as "unconfirmed."

Summary

nginx is the web entrance and distribution
PHP runs WordPress and creates HTML
MySQL saves articles, settings, etc.
Docker makes it easy to isolate and reproduce parts, but does not perform maintenance on your behalf
Back up WordPress images and DB at the same time
Monitor not only container startup but also public page and reservation flow
Updates are done layer by layer, and people check sales operations.

Please check Responsibility for operating WordPress on VPS to find out who will manage these.