Get Expired Transient

gistfile1.aw

/**
 * Used in front end requests to get the latest Tweet.
 *
 * @return bool|string
 */
function get_latest_tweet() {
	// Attempt to get the transient
	if ( $tweet = get_transient( 'my_latest_tweet' ) ) {
		return $tweet;

	// If it doesn't exist, try grabbing the backedup version in wp_options and reset the transient
	} elseif ( $tweet = get_option( 'my_latest_tweet' ) ) {
		set_transient( 'my_latest_tweet', $tweet );
		return $tweet;

	// As a last ditch effort, query for the latest tweet
	} else {
		if ( false !== ( $tweet = cache_latest_tweet() ) ) {
			return $tweet;
		} else {
			return false;
		}
	}
}

/**
 * Grabs the latest tweet.
 *
 * This function fires on an hourly interval, but can be called on
 * front end requests in the event that the transient or wp_option is
 * not available.
 *
 * @return bool|string
 */
function cache_latest_tweet() {
	if ( get_transient( 'retrieving_latest_tweet_lock' ) )
		return false;

	// Avoid multiple requests
	set_transient( 'retrieving_latest_tweet_lock', 1 );

	/* Not shown: Make call to Twitter API and assign latest Tweet to $tweet */

	// Save as both a transient and an option
	set_transient( 'my_latest_tweet', $tweet );
	if ( get_option( 'my_latest_tweet' ) )
		update_option( 'my_latest_tweet', $tweet );
	else
		add_option( 'my_latest_tweet', $tweet, '', 'no' );

	// Remove the lock
	delete_transient( 'retrieving_latest_tweet_lock' );
	return $tweet;
}

if ( ! wp_next_scheduled( 'schedule_cache_latest_tweet' ) )
	wp_schedule_event( time(), 'hourly', 'schedule_cache_latest_tweet' );
add_action( 'schedule_cache_latest_tweet', 'cache_latest_tweet' );