Simple WordPress Scheduled Task Structure

wp_schedule_task

<?php
add_action( 'wp', 'schedule_task' );
/* Let's schedule some tasks! */
function schedule_task() {
	if ( ! wp_next_scheduled( 'task_hook' ) ) {
		// Add scheduled daily task
		wp_schedule_event( time(), 'daily', 'task_hook');
	}
}
add_action( 'task_hook', 'function_to_run' );
/* Garbage collection for transient cache in wp_options table in db */
function function_to_run() {

	// Do stuff. 

}