Function to Delete Expired Transients in WordPress

The following function will delete all expired transients in WordPress.

(See here instead to delete all transients.)

PHP

/**
* Deletes all transients that have expired
*/
function isa_purge_expired_transients($older_than = '1 day', $safemode = true) {

	global $wpdb;
	$older_than_time = strtotime('-' . $older_than);

	/**
	* Only check if the transients are older than the specified time
	*/

	if ( $older_than_time > time() || $older_than_time < 1 ) {
		return false;
	}

	/**
	* Get all the expired transients
	*
	* @var mixed
	* @access public
	*/
	$transients = $wpdb->get_col(
	$wpdb->prepare( "
	SELECT REPLACE(option_name, '_transient_timeout_', '') AS transient_name
	FROM {$wpdb->options}
	WHERE option_name LIKE '\_transient\_timeout\__%%'
	AND option_value < %s
	", $older_than_time)
	);

	/**
	* If safemode is ON just use the default WordPress get_transient() function
	* to delete the expired transients
	*/

	if ( $safemode ) {
		foreach( $transients as $transient ) {
			get_transient($transient);
		}
	}

	/**
	* If safemode is OFF the just manually delete all the transient rows in the database
	*/

	else {
		$options_names = array();
		foreach($transients as $transient) {
			$options_names[] = '_transient_' . $transient;
			$options_names[] = '_transient_timeout_' . $transient;
		}
		if ($options_names) {
			$options_names = array_map(array($wpdb, 'escape'), $options_names);
			$options_names = "'". implode("','", $options_names) ."'";

			$result = $wpdb->query( "DELETE FROM {$wpdb->options} WHERE option_name IN ({$options_names})" );
			if (!$result) {
				return false;
			}
		}
	}

	return $transients;
}