Using WordPress ‘is_child_theme()’ PHP function

by

The is_child_theme() WordPress PHP function checks if a child theme is currently in use.

Usage

$is_child = is_child_theme();

Input: None

Output: Returns true if a child theme is in use, false otherwise.

Parameters

  • None

More information

See WordPress Developer Resources: is_child_theme()

Important Note: This function uses the TEMPLATEPATH and STYLESHEETPATH constants internally. If calling from a plugin, such as during plugin activation, there’s a chance these will be undefined. It is better to use: get_template_directory() !== get_stylesheet_directory()

Examples

Display a message if a child theme is in use

This code displays a message on the website if a child theme is currently active.

if (is_child_theme()) {
  echo 'This website is using a child theme.';
}

Enqueue child theme styles

This code enqueues the child theme’s style.css file if a child theme is in use.

function my_enqueue_styles() {
  if (is_child_theme()) {
    wp_enqueue_style('child-theme-style', get_stylesheet_uri());
  }
}
add_action('wp_enqueue_scripts', 'my_enqueue_styles');

Add custom functionality for child themes

This code adds custom functionality only when a child theme is active.

if (is_child_theme()) {
  function my_child_theme_function() {
    // Custom functionality for child themes
  }
  add_action('init', 'my_child_theme_function');
}

Add a custom class to the body if a child theme is in use

This code adds a custom CSS class to the body element if a child theme is active.

function my_child_theme_body_class($classes) {
  if (is_child_theme()) {
    $classes[] = 'using-child-theme';
  }
  return $classes;
}
add_filter('body_class', 'my_child_theme_body_class');

Modify a template part for child themes

This code modifies a template part for child themes, replacing the parent theme’s template-parts/content with template-parts/content-child.

function my_child_theme_template_part() {
  $template_part = 'template-parts/content';
  if (is_child_theme()) {
    $template_part = 'template-parts/content-child';
  }
  get_template_part($template_part);
}