wp-includes/theme.php:1808Retrieves the markup for a custom header.
stringfunction get_custom_header_markup() { if ( ! has_custom_header() && ! is_customize_preview() ) { return ''; } return sprintf( '<div id="wp-custom-header" class="wp-custom-header">%s</div>', get_header_image_tag() );}Introduced in 4.7.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/theme.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.