Wordpress cronjob every 5 seconds not working

Question

I've added following into my Wordpress functions.php file to send a mail every 5 seconds to the entered email address but it's not working. I've added some logging to check if the job runs the hook but it's just initializing it and thats it:

add_filter( 'cron_schedules', 'five_seconds_interval' );
function five_seconds_interval( $schedules ) {
    $schedules['five_seconds'] = array(
        'interval' => 5,
        'display'  => esc_html__( 'Alle 5 Sekunden' ),
    );

    return $schedules;
}

add_action('init', 'schedule_my_cron',10);
function schedule_my_cron(){
    error_log("schedule_my_cron()");
    wp_schedule_event(time(), 'five_seconds', 'my_job');
}

function my_job() {
    error_log("my_job()");
    wp_mail('test@localhost.de', 'Cronjob funktioniert!', 'LOL', 'Von IBims');
}

This is what I'm getting in my logfile:

[14-Nov-2018 17:31:24 UTC] schedule_my_cron()

I've also disabled the normal cronjob for Wordpress in my config file:

define( 'DISABLE_WP_CRON', true );

After this I've created a unix cronjob which works fine. So I'm expecting that when I run the unix cronjob every 5 seconds that I'm getting my mail sent to the address. Whats wrong?

Update

I can confirm that my custom schedule was added successfully, here is part of the output from wp get schedules() :

[five_seconds] => Array
    (
        [interval] => 5
        [display] => Alle 5 Sekunden
    )

Answer 1

According to the documentation for the function you need to use add_action() for the function being called on schedule, not the function doing the scheduling. The third parameter to wp_schedule_event() is the name of an action hook, not a function name. Try something like this:

register_activation_hook(__FILE__, 'schedule_my_cron');
add_action('init', 'schedule_my_cron',10);
function schedule_my_cron(){
    error_log("schedule_my_cron()");
    wp_schedule_event(time(), 'five_seconds', 'my_five_second_event');
}

add_action('my_five_second_event', 'my_job');
function my_job() {
    error_log("my_job()");
    wp_mail('test@localhost.de', 'Cronjob funktioniert!', 'LOL', 'Von IBims');
}