wp-includes/customize/class-wp-customize-custom-css-setting.php:65WP_Customize_Custom_CSS_Setting constructor.
$managerWP_Customize_Manager$idstring$argsarrayoptionalarray() public function __construct( $manager, $id, $args = array() ) { parent::__construct( $manager, $id, $args ); if ( 'custom_css' !== $this->id_data['base'] ) { throw new Exception( 'Expected custom_css id_base.' ); } if ( 1 !== count( $this->id_data['keys'] ) || empty( $this->id_data['keys'][0] ) ) { throw new Exception( 'Expected single stylesheet key.' ); } $this->stylesheet = $this->id_data['keys'][0]; }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/customize/class-wp-customize-custom-css-setting.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.