Add note about wp_next_scheduled() in wp_schedule_event(). See #14668

git-svn-id: https://develop.svn.wordpress.org/trunk@16690 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/cron.php

@@ -50,6 +50,8 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
  * Valid values for the recurrence are hourly, daily and twicedaily.  These can
  * be extended using the cron_schedules filter in wp_get_schedules().
  *
+ * Use wp_next_scheduled() to prevent duplicates
+ *
  * @since 2.1.0
  *
  * @param int $timestamp Timestamp for when to run the event.
@@ -402,4 +404,4 @@ function _upgrade_cron_array($cron) {
 	$new_cron['version'] = 2;
 	update_option( 'cron', $new_cron );
 	return $new_cron;
-}
+}