Only show metabox when date-value in other metabox is over?

probably a weird question.
I’m using the custom MetaBox and CustomFields Class by jaredatch on Github.

I have this “event-date” metabox:

$meta_boxes[] = array(
        'id'         => 'event_date',
        'title'      => 'Event Date',
        'pages'      => array( 'wr_event', ),
        'context'    => 'normal',
        'priority'   => 'high',
        'fields'     => array(
            array(
                'name' => 'Test Date Picker (UNIX timestamp)',
                'desc' => 'field description (optional)',
                'id'   => $prefix . 'event_date',
                'type' => 'text_date_timestamp',
            )
        ),
    );

I have a second metabox called “event-review”

$meta_boxes[] = array(
    'id'         => 'wr_event_review',
    'title'      => 'Event Review',
    'pages'      => array( 'wr_event', ), // Post type
    'context'    => 'normal',
    'priority'   => 'high',
    'show_names' => true, // Show field names on the left
    'fields'     => array(
        array(
            'name'    => 'Event Review',
            'id'      => $prefix . 'event_wysiwyg',
            'type'    => 'wysiwyg',
            'options' => array( 'textarea_rows' => 5, ),
        )
    ),
);

I wonder if it’s possible to show the event-review metabox only when the date is over?

Something like…

if ( date('U') > date('U', $_POST["_wr_event_date"] ) ) {
     $meta_boxes[] = array(
        'id'         => 'wr_event_review',
        'title'      => 'Event Review',

However I have no idea if this is even possible or even how I can get the current event_date that is in the input.

Any thoughts on this?

Not sure about the linked class – it seems they collect metaboxes immediately and so there is no information regarding what post is being viewed.

In general though – yes it is possible. To add a metabox:

add_action( 'add_meta_boxes', 'myplugin_add_my_custom_box',10,2);

See the source code here. This add_meta_boxes hook passes two variables: the post type and the post object. You can use the post to get the post meta and then call add_meta_box where appropriate.

function myplugin_add_my_custom_box($post_type,$post){
     //Get event date as a timestamp
     $event_date = (int) get_post_meta($post->ID,'_wr_event_date',true);

     //Check date exists and is in the past. If not, return: don't add metabox.
     if( empty($event_date) || current_time('timestamp') < $event_date)
         return;

     add_meta_box( 
        'myplugin_sectionid',
        __( 'My Post Section Title', 'myplugin_textdomain' ),
        'myplugin_metabox_callback',
        'event' 
    );      
}

You’ll notice there is also a add_meta_boxes_{$post_type} hook – this is more efficient if you want to just add it to ‘event_cpt’ post types:

     add_action( 'add_meta_boxes_event_cpt', 'myplugin_add_my_custom_box',10,1);

In this case your callback only includes the $post as an argument!

Note: Avoid using php date/time functions: this will, by default, always have the timezone set to UTC. If you want the current date/time in the blogs timezone using something like current_time()