For cron jobs, WordPress comes with a few built-in schedules to add your event to – hourly, twicedaily, daily and (since WordPress 5.4) weekly. All of them run on a defined interval. Hourly runs every hour, twicedaily runs every 12 hours, daily runs every 24 hours and weekly runs every 7 days. To add a new schedule time, the cron_schedules filter is used. The code below will add three new cron schedules ( in_per_minute, in_per_ten_minute, three_hourly ).

Add Custom Schedules

add_filter( 'cron_schedules', 'w4dev_cron_schedules');
function w4dev_cron_schedules( $schedules )
{
	$schedules['in_per_minute'] = array(
		'interval' => 60,
		'display' => 'In Every Minute'
	);
	$schedules['in_per_ten_minute'] = array(
		'interval' => 60 * 10,
		'display' => 'In Every Ten Minutes'
	);
	$schedules['three_hourly'] = array(
		'interval' => 60 * 60 * 3,
		'display' => 'Once in Three Hours'
	);

	return $schedules;
}

Reference: interval is measured in seconds. 2 minutes = 60 * 2 sec. display is the display label name for the schedule. Note that we add our schedules to the $schedules array instead of returning a new array, otherwise we would remove schedules registered by other plugins.

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Using the new schedule

First you will need to register an event for the schedule. You can register multiple events for one schedule. Upon registering an event with a schedule, a new action hook becomes available.

Schedule an Event

if( !wp_next_scheduled('w4dev_one_minute_event') )
{
	wp_schedule_event( time(), 'in_per_minute', 'w4dev_one_minute_event' );
}

This code will schedule a new event w4dev_one_minute_event to be run every minute. That means, each minute, an action hook – w4dev_one_minute_event will be available once to call.

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Call a function on scheduled event

You can hook into the event with your function. You can even hook multiple times using multiple functions.

function w4dev_one_minute_job_cron()
{
    // your code here
}
add_action( 'w4dev_one_minute_event', 'w4dev_one_minute_job_cron' );

That’s it. All of the above code can be placed in your theme’s functions.php file or in a plugin.