body_class( string|string[] $css_class = '' )
- Since
- 2.8.0
- Source
wp-includes/post-template.php:620
Compatibility
- WordPress
- since 2.8.0
- 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.
Parameters
$css_classstring|string[]optional- Space-separated string or array of class names to add to the class list. Default empty.Default:
''
Performance profile
How much work a call to body_class() 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
- Heavy
- Scaling
- Constant
- Instructions
- 12
- Plugin surface
- None
- Called by
- 2
Reaches the database via get_pages().
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 12.
Nothing here hands control to plugin code.
2 places in core call this, so the cost is paid more often than your own code shows.
What it touches
- hookthird-party callbacks
apply_filters()one call below body_class() - querycontent query
get_pages()one call below body_class()
Further down the call graph this can also reach option, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.
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 body_class() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 12 | get_body_class(), esc_attr() |
Across PHP versions
| PHP | Compiled | Executed | Branches | Notes |
|---|---|---|---|---|
| 8.6-dev | 12 | 12 | 0 | |
| 8.5 | 12 | 12 | 0 | |
| 8.4 | 12 | 12 | 0 | 3 fewer instructions than PHP 8.3 |
| 8.3 | 15 | 15 | 0 | |
| 8.2 | 15 | 15 | 0 | |
| 8.1 | 15 | 15 | 0 | |
| 7.4 | 15 | 15 | 0 |
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.
Uses · 2
- esc_attr()Escaping for HTML attributes.
- get_body_class()Retrieves an array of the class names for the body element.
Used by · 2
- WP_REST_Widget_Types_Controller::render_legacy_widget_preview_iframe()Renders a page containing a preview of the requested Legacy Widget block.
- handle_legacy_widget_preview_iframe()Intercepts any request with legacy-widget-preview in the query param and, if set, renders a page containing a preview of the requested Legacy Widget block.
Source code
function body_class( $css_class = '' ) { // Separates class names with a single space, collates class names for body element. echo 'class="' . esc_attr( implode( ' ', get_body_class( $css_class ) ) ) . '"';}Changelog
Introduced in 2.8.0. 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 6.7.7 tag, from
src/wp-includes/post-template.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.