is_child_theme(): bool
- Since
- 3.0.0, 6.5.0
- Source
wp-includes/theme.php:163
Compatibility
- WordPress
- since 6.5.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Return value
bool- True if a child theme is in use, false otherwise.
Performance profile
How much work a call to is_child_theme() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Trivial
- Scaling
- Constant
- Instructions
- 4
- Plugin surface
- None
- Called by
- 8
Touches nothing outside its own arguments.
No loop in the body: the same number of instructions runs whatever you pass in.
Executed per call on PHP 8.5. The body compiles to 4.
Nothing here hands control to plugin code.
8 places in core call this, so the cost is paid more often than your own code shows.
What one call costs · 1 distinct outcome
One number would be a lie: the work depends on which branch runs. These are every distinct cost is_child_theme() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 4 | none |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 4 instructions, 4 executed per call, 0 branches. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Used by · 8
- WP_Customize_Manager::prepare_starter_content_attachments()Prepares starter content attachments.
- WP_Site_Health::get_test_theme_version()Tests if themes are outdated, or unnecessary.
- get_block_asset_url()Gets the URL to a block asset.
- get_body_class()Retrieves an array of the class names for the body element.
- get_editor_stylesheets()Retrieves any registered editor stylesheet URLs.
- locate_template()Retrieves the name of the highest priority template file that exists.
- validate_current_theme()Checks that the active theme has the required files.
- wp_get_active_and_valid_themes()Retrieves an array of active and valid themes.
Source code
function is_child_theme() { global $wp_stylesheet_path, $wp_template_path; return $wp_stylesheet_path !== $wp_template_path;}Changelog
Introduced in 3.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 6.9.7 tag, from
src/wp-includes/theme.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.