public static function get_anon_id() {
		static $anon_id = null;

		if ( ! isset( $anon_id ) ) {

			// Did the browser send us a cookie?
			if ( isset( $_COOKIE['tk_ai'] ) ) {
				$anon_id = sanitize_text_field( wp_unslash( $_COOKIE['tk_ai'] ) );
			} else {

				$binary = '';

				// Generate a new anonId and try to save it in the browser's cookies.
				// Note that base64-encoding an 18 character string generates a 24-character anon id.
				for ( $i = 0; $i < 18; ++$i ) {
					$binary .= chr( wp_rand( 0, 255 ) );
				}

				$anon_id = 'woo:' . base64_encode( $binary );
			}
		}

		return $anon_id;
	}