Setup wp_schedule_event within a custom plugin

Question

First of all: if you haven’t read it already, please check the official documentation on WP-Cron.

The problem in your code is this line

    add_action( 'setupCronJob_whatToMine', 'setupCronJob');

You’re defining a new action setupCronJob_whatToMine and add the setupCronJob method to it. But as this is a custom action you just created, it will never be called (eg via do_action('setupCronJob_whatToMine');).

So instead of adding it to an action, you can call setupCronJob() directly to set up the event scheduling.

You can do it in the init action. However, this will add the logic to every page load, which is unnecessary. A cron like needs to be set up only once.

So I’d add the Cron in the activation hook (and don’t forget to remove it in the deactivation hook).

Simple code example:

MyPlugin.php

register_activation_hook( __FILE__, array(My_Plugin::class, 'activate') );
register_deactivation_hook( __FILE__, array(My_Plugin::class, 'deactivate') );

class MyPlugin
{

    public static function activate()
    {
        WhatToMineAPI::setupCronJob();
    }

    public static function deactivate()
    {
        WhatToMineAPI::unsetCronJob();
    }

    // your other methods

}

WhatToMineAPI.php

class WhatToMineAPI
{

    const CRON_HOOK = 'update_whatToMine_api';

    public static function setupCronJob()
    {
        //Use wp_next_scheduled to check if the event is already scheduled
        $timestamp = wp_next_scheduled( self::CRON_HOOK );

        //If $timestamp === false schedule daily backups since it hasn't been done previously
        if( $timestamp === false ){
            //Schedule the event for right now, then to repeat daily using the hook 'update_whatToMine_api'
            wp_schedule_event( time(), 'twicedaily', self::CRON_HOOK );
        }
    }

    public static function unsetCronJob()
    {
        // Get the timestamp for the next event.
        $timestamp = wp_next_scheduled( self::CRON_HOOK );
        wp_unschedule_event( $timestamp, self::CRON_HOOK );
    }

    public function __construct()
    {
        add_action(self::CRON_HOOK, array($this, 'updateWhatToMineAPI'));
    }

    public function updateWhatToMineAPI()
    {
        $client = new GuzzleHttp\Client();
        $response = $client->request('GET', $whatToMineURL);
    }

}

Side note: When working with classes, you need to beware. Either use add_action('...', array($this, 'methodName')) but then you need $this or similar defined.

Alternatively you can use static methods like so add_action('...', array(MySuperClass::class, 'staticMethodName'))

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