wp-content/themes/twentytwentyone/classes/class-twenty-twenty-one-customize.php:158Sanitizes a boolean for checkbox.
$checkedbooloptionalnullbool public static function sanitize_checkbox( $checked = null ) { return (bool) isset( $checked ) && true === $checked; }Introduced in Twenty Twenty-One 1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-content/themes/twentytwentyone/classes/class-twenty-twenty-one-customize.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.