Still trying to figure out this thing.
I’m trying to turn the date into a timestamp, hooking on “save_post”. Basically, when the event is saved, the start-date and end-date are translated into timestamp and saved into the post-meta fields “timestamp-start-date” and “timestamp-end-date”.
In my metaboxes for events, I added two hidden fields.

Now, the issue I have is:
– if I put the two hidden fields (named “timestamp-start-date” and “timestamp-end-date”), the timestamps are NOT saved (I wonder if they could be overridden with a null value after my function has just set them, but supposedly save_post is called AFTER the post has been saved).
– if I remove those hidden fields, the timestamps appear nicely in the database (but of course, disappear from the picklist form).

I guess I could do without the hidden fields, but does that mean I need to destroy those timestamps when an event is deleted? Or does WP remove all “post_meta” associated with the deleted post?

Here is my code:

The hidden fields:

piklist('field', array(
 'type' => 'hidden'
 ,'field' => 'start-date-timestamp'	 
 ));
 
 piklist('field', array(
  'type' => 'hidden'
  ,'field' => 'end-date-timestamp'
  ));	

The hook to save the timestamp:

function save_events_meta( $post_id, $post, $update ) {
	
    $start_date = $_REQUEST['_post_meta']['event_dates']['start-date'][0];
    $end_date = $_REQUEST['_post_meta']['event_dates']['end-date'][0]; 
	
    if ( isset( $start_date ) ) {
        update_post_meta( $post_id, 'start-date-timestamp', strtotime($start_date));
    }

    if ( isset( $end_date ) ) {
        update_post_meta( $post_id, 'end-date-timestamp', strtotime($end_date));
    }
}
add_action( 'save_post_events', 'save_events_meta', 10, 3 );

To sum-up: “save_events_meta” works if I don’t add the hidden field to the event metaboxes. Stop working if I put back the hidden fields.

Any help welcome 🙂

Thank you everyone 🙂
Well, it makes sense to store a date as a String if all you do is to display it. If you need those dates to do something, like comparing/sorting them, it’s a bit less convenient. I wouldn’t mind storing a datetime object and formatting it at display, but it’s not convenient with Piklist: the “dateformat” you choose for picklist is the format the date is going to be displayed in the html form after selecting the date in the calendar. Not super user friendly 🙂

Anyway, this is the code I use the request sorting by start date:

/* Sort the events to appear sorted by starting date */
function get_events( $query ) {
	if ( is_post_type_archive('events') && $query->is_main_query()) { 
		$query->query_vars['meta_key'] = 'starting_on';
		$query->query_vars['orderby'] = 'meta_value';
		$query->query_vars['order'] = 'ASC';
	}
	return $query;
}
add_filter( 'pre_get_posts', 'get_events' );

If I follow you, Steve, I should use a custom function here to sort my custom posts (= events) ?
Though if I do, each time the page is requested, if posts date is going to be processed for the sorting. Isn’t is consuming?

No, it doesn’t. I comment out PiklistHelper by default to test.

Oops, can’t attach ZIP or PHP apparently.
You can download the plugin here.

Ok, I’ve been investigating a bit. Here is what I got so far:

First, I had made a mistake in my custom validation declaration (my validation rule was called “html”. I called it “valid_float”. I fixed this, but it didn’t make it work.
What did was to increase the priority parameter when calling the “add_filter” function. The documentation usually show “11”, but it only worked when I put it to 12. I don’t know why.

  add_filter('piklist_validation_rules', 'check_valid_float', 12);
  function check_valid_float()
  {
    $validation_rules = array(
      'valid_float' => array( 
        'rule' => "/^[1-9]+(.\d+)?(.\d+)?/"
        ,'message' => __('is not a valid number.')
      )
    ); 
    return $validation_rules;
  }

Now, the numeric validation works on custom post forms BUT:
– it doesn’t work at all on setting forms.
– it doesn’t work anymore if I declare another validation rule (with another name and function name, of course).

Any help is welcome, really. Or a workaround for validating piklist forms another way.

Oops, I didn’t see that :/

Thank you very much for your quick answer. It works perfect now.

Oh, ok! It works perfectly, thank you very much!
And now I understand why the arrays : all entries info are aggregated by fields. I was thinking the other way around, more object-oriented of json-like, where each entry would contain its own info.
It’s crystal clear, now, thank you very much for your help!