What Is a Child Theme

A child theme is a WordPress theme that depends on another theme (the parent). WordPress loads the parent theme, then overlays the child theme on top. You use the child theme to add versioned CSS/JS and small PHP changes without editing vendor code.

warning

If you edit functions.php on production and introduce a PHP syntax error, you can take the site down. Use staging and keep a rollback command ready.

What a Child Theme Is (and What It Is Not)

Item	It is	It is not
Child theme	Your update-safe customization layer	A replacement for plugins
Parent theme	Vendor code you update (GeneratePress)	Where you should put custom changes
Template override	A copied template in the child theme	The default way to customize everything

How Inheritance Works

There are two main inheritance paths:

1. Templates: WordPress checks the child theme first, then falls back to the parent.
2. Behavior: your child theme registers hooks/filters, and WordPress executes them during the request.

flowchart TD
  WP[WordPress] --> PARENT[GeneratePress parent theme]
  PARENT --> CHILD[Child theme]
  CHILD --> HOOKS[Hooks/filters in functions.php]
  CHILD --> TPL["Template overrides (optional)"]
  TPL -->|fallback| PTPL[Parent templates]
  HOOKS --> OUT[Rendered output]
  PTPL --> OUT

Where Child Themes Live on Disk

Typical paths on an Ubuntu server:

Path	Purpose
/var/www/html/wp-content/themes/generatepress/	Parent theme (vendor)
/var/www/html/wp-content/themes/generatepress-child/	Child theme (yours)
/var/www/html/wp-content/themes/generatepress-child/functions.php	Hook/filter customizations
/var/www/html/wp-content/themes/generatepress-child/style.css	Metadata + child styles

List parent/child theme folders

cd /var/www/html
ls -lah wp-content/themes | rg -n "generatepress$|generatepress-child$" || true

When You Should Use a Child Theme

Use a child theme when you need versioned, deployable changes:

• Custom PHP (hooks/filters, shortcodes, integrations)
• A small asset pipeline (CSS/JS) you want to ship through Git
• A repeatable deployment workflow across staging/production

Use Elements and the Customizer when you do not need code:

• Conditional headers/CTAs
• Layout changes by context
• Design system settings (typography/colors/spacing)

note

The best GeneratePress workflow is usually: Customizer + blocks first, Elements second, child theme only when code is required.

Minimal Child Theme: The Two Files That Matter

At minimum, a child theme needs a valid style.css header that points to the parent theme.

wp-content/themes/generatepress-child/style.css (minimal header)

/*
Theme Name: GeneratePress Child
Template: generatepress
Version: 1.0.0
*/

And a functions.php that can enqueue styles or register hooks.

wp-content/themes/generatepress-child/functions.php (minimal scaffold)

<?php
add_action( 'wp_enqueue_scripts', function () {
    // Optional: enqueue a child stylesheet.
    wp_enqueue_style(
        'gp-child',
        get_stylesheet_uri(),
        [],
        '1.0.0'
    );
} );

Troubleshooting Quick Checks

Symptom	Likely cause	Fast check
Child theme won't activate	Missing/incorrect Template header	rg -n "^Template:" style.css
Styles not applying	Cache or enqueue issue	Purge cache, check page source for CSS
Site white screens	PHP error	Check /usr/local/lsws/logs/error.log

Quick Reference

Confirm active parent/child relationship

cd /var/www/html
wp option get stylesheet
wp option get template

What's Next

• Next: Why Use a Child Theme
• Later: Create Child Theme via CLI