Caching with a "Backup"

gistfile1.aw

<?php
function get_hottest_cities( $force = false ) {
	$hottest_cities = get_transient( 'zdt-hottest-cities' );
	if ( false === $hottest_cities || $force ) {
		if ( $force ) {
			$hottest_cities = retrieve_hottest_cities();

			if ( $hottest_cities ) {
				set_transient( 'zdt-hottest-cities', $hottest_cities );

				if ( get_option( 'zdt-hottest-cities' ) )
					update_option( 'zdt-hottest-cities', $hottest_cities );
				else
					add_option( 'zdt-hottest-cities', $hottest_cities, '', 'no' );
			}
		} else {
			$backup = get_option( 'zdt-hottest-cities', array() );
			set_transient( 'zdt-hottest-cities', $backup );
			wp_schedule_single_event( time(), 'zdt_refresh_hottest_cities' );
		}
	}

	return $hottest_cities;
}