WP_REST_Server::get_raw_data()

	public static function get_raw_data() {
		global $HTTP_RAW_POST_DATA;

		/*
		 * A bug in PHP < 5.2.2 makes $HTTP_RAW_POST_DATA not set by default,
		 * but we can do it ourself.
		 */
		if ( ! isset( $HTTP_RAW_POST_DATA ) ) {
			$HTTP_RAW_POST_DATA = file_get_contents( 'php://input' );
		}

		return $HTTP_RAW_POST_DATA;
	}