Managing scheduled tasks

Question

I want users of my plugin to be able to define whether a task operates daily, twice daily, hourly or not at all as per the standard WP set-up. I'm storing these as 'daily', 'twicedaily', 'hourly' or '' in the option obr_scheduled_interval.

The problem is that the task that I want 'obr_grab' runs every time there's a page visit rather than every time there's a page visit after the selected time period.

These are the relevant bits of code from the class.

function __construct(){
    register_activation_hook(__FILE__, array(&$this, 'obr_activate_scheduled_task'));
    add_action('obr_scheduled_task', array(&$this, 'obr_activate_scheduled_task'));
    add_shortcode('obr_grab', array(&$this, 'obr_grab'));
    register_deactivation_hook(__FILE__, array(&$this, 'obr_deactivate_scheduled_task'));
}

function obr_activate_scheduled_task() {
    // function to activate the scheduled task (if there is one);
    if (wp_next_scheduled('obr_scheduled_task')){
        wp_clear_scheduled_hook('obr_scheduled_task');
    }
    $interval = get_option('obr_scheduled_interval');
    if (strlen($interval) > 0){
        wp_schedule_event(time(), $interval, 'obr_scheduled_task');
    }
}

function obr_scheduled_task(){
    // if called we need to use the grab function
    $this->obr_grab();
}

function obr_deactivate_scheduled_task(){
    // clear the schedule on deactivation
    wp_clear_scheduled_hook('obr_scheduled_task');
}       

I've looked at core control but there are only two standard jobs there: wp_scheduled_auto_draft_delete and wp_scheduled_delete

All help much appreciated!

Answer 1

It looks to me that this line

add_action('obr_scheduled_task', array(&$this, 'obr_activate_scheduled_task'));

should be

add_action('obr_scheduled_task', array(&$this, 'obr_scheduled_task'));

otherwise you are re-scheduling on every page visit.

Edit:

Here is a logger that can be useful when debugging wp-cron:

function my_logger($var){
    $logfile="/tmp/logger.txt"; // EDIT this to your needs
    file_put_contents($logfile, date("Y-m-d: H:i:s",time())." --- ".print_r($var, true)."\n", FILE_APPEND);
}

You can use it inside your class functions with relevant debug messages,

 my_logger("My Class construction");
 my_logger("Running the cron function");

and the logfile will look like this:

2013-02-20: 14:00:43 --- My Class construction
2013-02-20: 14:00:53 --- Running the cron function

Hope this helps.