Wordpress cronjob every 3 minutes

You need to use add_action() to hook your function to the scheduled event.

add_action( 'isa_add_every_three_minutes', 'every_three_minutes_event_func' );

Here is the full code.

// Add a new interval of 180 seconds// See http://codex.wordpress.org/Plugin_API/Filter_Reference/cron_schedulesadd_filter( 'cron_schedules', 'isa_add_every_three_minutes' );function isa_add_every_three_minutes( $schedules ) {    $schedules['every_three_minutes'] = array(            'interval'  => 180,            'display'   => __( 'Every 3 Minutes', 'textdomain' )    );    return $schedules;}// Schedule an action if it's not already scheduledif ( ! wp_next_scheduled( 'isa_add_every_three_minutes' ) ) {    wp_schedule_event( time(), 'every_three_minutes', 'isa_add_every_three_minutes' );}// Hook into that action that'll fire every three minutesadd_action( 'isa_add_every_three_minutes', 'every_three_minutes_event_func' );function every_three_minutes_event_func() {    // do something}?>

seems you forgot to use the command add_action()

See this exemple: http://wpguru.co.uk/2014/01/how-to-create-a-cron-job-in-wordpress-teach-your-plugin-to-do-something-automatically/

First of its important where this code is in, is it in your functions.php for your theme? Or is it a custom plugin your developing?

Through my experience its both easier to debug and activate cron through a custom plugin, using activation hooks to activate and deactivate events. I have had hard times activating cron events through functions php before, I prefer activating these events through custom plugins.

I would start with a plugin structure like this:

• /my-cron-plugin
• /my-cron-plugin/index.php
• /my-cron-plugin/my-cron-plugin.php

index.php contents:

<?php // silence is golden

my-cron-plugin.php contents:

<?php/** * Plugin name: My Custom Cron Plugin * Description: Simple WP cron plugin boilerplate. * Author: Your name * Version: 0.1 */// Security reasons...if( !function_exists( 'add_action' ) ){    die('...');}// The activation hookfunction isa_activation(){    if( !wp_next_scheduled( 'isa_add_every_three_minutes_event' ) ){        wp_schedule_event( time(), 'every_three_minutes', 'isa_add_every_three_minutes_event' );    }}register_activation_hook(   __FILE__, 'isa_activation' );// The deactivation hookfunction isa_deactivation(){    if( wp_next_scheduled( 'isa_add_every_three_minutes_event' ) ){        wp_clear_scheduled_hook( 'isa_add_every_three_minutes_event' );    }}register_deactivation_hook( __FILE__, 'isa_deactivation' );// The schedule filter hookfunction isa_add_every_three_minutes( $schedules ) {    $schedules['every_three_minutes'] = array(            'interval'  => 180,            'display'   => __( 'Every 3 Minutes', 'textdomain' )    );    return $schedules;}add_filter( 'cron_schedules', 'isa_add_every_three_minutes' );// The WP Cron event callback functionfunction isa_every_three_minutes_event_func() {    // do something}add_action( 'isa_add_every_three_minutes_event', 'isa_every_three_minutes_event_func' );

After having setup this plugin, the event should be activated upon plugin activation. To test if its working use this plugin: https://wordpress.org/plugins/wp-crontrol/

One other good resource to understand how WP cron work is: https://developer.wordpress.org/plugins/cron/