Code for a wp_schedule_single_event Tutorial.

schedule-event-tutorial.php

<?php

/**
 * Plugin Name: Schedule Event Tutorial
 * Description: Schedules single event to uncheck a checkbox on a custom Menu page
 * Version: 0.1
 * Author: John Regan
 * Author URI: http://johnregan3.me
 * Text Domain: setjr3
 * License: GPLv2+
 */

/**
 * Copyright (c) 2013 X-Team (http://x-team.com/)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2 or, at
 * your discretion, any later version, as published by the Free
 * Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */


/**
 * This class is where you can see Scheduled Events in action.
 *
 * Here, the old scheduled event is unscheduled and the new event is set.
 */
class Schedule_Event_Tutorial {

	/**
	 * Registers our 'uncheck_event_hook" action hook that fires our un-checking action.
	 */
	static function setup() {
		// Scheduled Event Hook
		add_action( 'uncheck_event_hook', array( __CLASS__, 'uncheck_checkbox' ) );
	}


	/**
	 * On settings save, Update scheduled event time.
	 *
	 * Begin by removing any scheduled event on our 'uncheck_event_hook' hook.
	 * Then, we format the saved time to Unix.
	 * Finally, we schedule the event.
	 *
	 * Typically, this could be fired when a post is saved ('save_post' hook, for instance),
	 * but it's not really that easy on an options page like this one.
	 *
	 * @action 'load-{page}'
	 * See Schedule_Event_Tutorial_Setup::menu_page()
	 */
	static function schedule_event() {
		if ( ! isset( $_GET['settings-updated'] ) )
			return;

		// Remove any scheduled event on this hook
		$scheduled_event = wp_next_scheduled( 'uncheck_event_hook' );
		if ( $scheduled_event !== false ) {
			wp_unschedule_event( $scheduled_event, 'uncheck_event_hook' );
		}

		// Schedule the event to uncheck the checkbox
		$exp_time = self::expiration_time();
		if ( is_numeric( $exp_time ) ) {
			wp_schedule_single_event( $exp_time, 'uncheck_event_hook' );
		}
	}


	/**
	* Fetches and formats the saved expiration time
	*
	* Get expiration time from options, set it according to the local timezone
	* then format it as Unix time.
	*
	* @return int  $time  Unix-formatted time string
	*/
	static function expiration_time() {
		$exp_time = get_option( 'setjr3_time' );
		$time     = ( ! empty( $exp_time ) ) ? $exp_time : null ;
		// If no time is set, exit.
		if ( is_null( $time ) )
			return false;

		$tz_local = new DateTimeZone( get_option( 'timezone_string' ) );
		$time     = new DateTime( $time, $tz_local );
		$time     = (int)$time->format('U');

		return $time;
	}


	/**
	 * The actual un-checking of the checkbox
	 *
	 * Fires on 'uncheck_event_hook' action, set in setup() above.
	 *
	 * @action 'uncheck_event_hook'
	 */
	static function uncheck_checkbox() {
		update_option( 'setjr3_checkbox', null );
	}

} // End class Schedule_Event_Tutorial




/**
 * Set up the Tutorial
 *
 * The content of this class simply sets up the tutorial form.
 * If you find it confusing, just ignore it.
 */
class Schedule_Event_Tutorial_Setup {

	/**
	 * Add our actions/filter
	 */
	static function setup() {
		$plugin = plugin_basename(__FILE__);
		add_filter( "plugin_action_links_$plugin", array( __CLASS__, 'tutorial_link' ) );
		// add action for Menu page
		add_action( 'admin_menu', array( __CLASS__, 'menu_page' ) );
		// add action for Settings
		add_action( 'admin_init', array( __CLASS__, 'settings' ) );

		// Run our Schedule_Event_Tutorial class above
		Schedule_Event_Tutorial::setup();

		// Clean up when this plugin is uninstalled
		register_uninstall_hook( __FILE__, array( __CLASS__, 'uninstall' ) );
	}


	/**
	 * Print direct link to Tutorial Admin Page
	 *
	 * Fetches array of links generated by WP Plugin admin page ( Deactivate | Edit )
	 * and inserts a link to the Custom CSS admin page
	 *
	 * @param  array  $links  Array of links generated by WP in Plugin Admin page.
	 * @return array  $links  Array of links to be output on Plugin Admin page.
	 */
	static function tutorial_link( $links ) {
		$settings_page = '<a href="' . admin_url( 'admin.php?page=schedule-event-tutorial.php' ) .'">Tutorial</a>';
		array_unshift( $links, $settings_page );
		return $links;
	}


	/**
	 * Create Admin Menu Page
	 *
	 * Also fires action to Schedule the Event when page reloads.
	 * see Schedule_Event_Tutorial::schedule_event()
	 */
	static function menu_page() {
		$slug = add_menu_page( __( 'Schedule Event Tutorial', 'setjr3' ), __( 'Schedule Event Tutorial', 'setjr3' ), 'manage_options', basename(__FILE__), array( __CLASS__, 'render_tutorial_page' ) );
		add_action( 'load-' . $slug, array( 'Schedule_Event_Tutorial', 'schedule_event' ) );
	}


	/**
	 * Settings Page setup
	 *
	 * For more info: http://codex.wordpress.org/Settings_API
	 */
	static function settings() {
		register_setting( 'setjr3_settings_group', 'setjr3_checkbox' );
		register_setting( 'setjr3_settings_group', 'setjr3_time' );
		add_settings_section( 'setjr3_section', '', '', __FILE__ );
		add_settings_field( 'checkbox', __( 'Checkbox', 'setjr3' ), array( __CLASS__, 'checkbox' ), __FILE__, 'setjr3_section' );
		add_settings_field( 'expiration_time', __( 'Expiration Time', 'setjr3' ), array( __CLASS__, 'expiration_time' ), __FILE__, 'setjr3_section' );
	}


	/**
	 * Render Checkbox
	 */
	static function checkbox() {
		$checkbox_value = get_option( 'setjr3_checkbox' );
		echo '<input type="checkbox" name="setjr3_checkbox" value="1" ' . checked( 1, $checkbox_value, false ) . '/>&nbsp;&nbsp;<span class="description">This checkbox will uncheck after the expiration time set below.</span>';
	}


	/**
	 * Render Date Input
	 */
	static function expiration_time() {
		$exp_time       = get_option( 'setjr3_time' );
		$exp_time_value = ( ! empty( $exp_time ) ) ? $exp_time : substr_replace( current_time( 'mysql' ), 'T', 10, 1 ) ;
		echo '<input name="setjr3_time" type="datetime-local" value="' . $exp_time_value .'" step="1" />';
	}


	/**
	 * Render Menu Page
	 */
	static function render_tutorial_page() {
		$curr_time      = substr_replace( current_time( 'mysql' ), 'T', 10, 1 );
		$exp_time       = get_option( 'setjr3_time' );
		$exp_time_value = ( ! empty( $exp_time ) ) ? $exp_time : 'Not set' ;
		?>
		<div class="wrap">
			<h2><?php echo __( 'Schedule Event Tuorial', 'setjr3') ?></h2>
			<?php if ( isset( $_GET['settings-updated'] ) ) { ?>
				<div id="message" class="updated">
					<p><strong><?php _e( 'Settings saved.', 'setjr3' ) ?></strong></p>
				</div>
			<?php } ?>
			<p>
				<?php _e( 'This is a tutorial demonstrating how to Schedule Events.<br />Begin by checking the checkbox below, then set a time for the checkbox to become unchecked.<br />Then, on the next page refresh after that time, the checkbox will be unchecked.', 'setjr3' ) ?>
			</p>
			<p>
				<code><?php _e( 'Current Time', 'setjr3' ) ?>: <?php echo $curr_time ?></code><br />
				<code><?php _e( 'Uncheck Time', 'setjr3' ) ?>: <?php echo $exp_time_value ?></code>
			</p>
			<form method="post" action="options.php" enctype="multipart/form-data">
				<?php settings_fields( 'setjr3_settings_group' ) ?>
				<?php do_settings_sections( __FILE__ ) ?>
				<?php submit_button() ?>
			</form>
		</div>
		<?php
	}


	/**
	 * Cleanup on unistnall
	 */
	static function uninstall() {
		unregister_setting( 'setjr3_settings_group', 'setjr3_checkbox' );
		unregister_setting( 'setjr3_settings_group', 'setjr3_time' );
	}

}

add_action( 'plugins_loaded', array( 'Schedule_Event_Tutorial_Setup', 'setup' ) );