function __construct($id = '', $output = 'OBJECT')
 {
     $this->id = $id;
     $this->output = $output;
     $this->details = get_post($this->id, $this->output);
     $tickets = new TC_Tickets_Instances();
     $fields = $tickets->get_tickets_instances_fields();
     foreach ($fields as $field) {
         if (!isset($this->details->{$field['field_name']})) {
             $this->details->{$field['field_name']} = get_post_meta($this->id, $field['field_name'], true);
         }
     }
 }
<?php

$tickets_instances = new TC_Tickets_Instances();
$page = $_GET['page'];
if (isset($_GET['action']) && $_GET['action'] == 'delete') {
    if (!isset($_POST['_wpnonce'])) {
        check_admin_referer('delete_' . $_GET['ID']);
        if (current_user_can('manage_options') || current_user_can('delete_tickets_cap')) {
            $ticket_instance = new TC_Ticket_Instance((int) $_GET['ID']);
            $ticket_instance->delete_ticket_instance();
            $message = __('Attendee and Ticket data has been successfully deleted.', 'tc');
        } else {
            $message = __('You do not have required permissions for this action.', 'tc');
        }
    }
}
if (isset($_GET['page_num'])) {
    $page_num = (int) $_GET['page_num'];
} else {
    $page_num = 1;
}
if (isset($_GET['s'])) {
    $attendeesearch = $_GET['s'];
} else {
    $attendeesearch = '';
}
$wp_tickets_instances_search = new TC_Tickets_Instances_Search($attendeesearch, $page_num);
$fields = $tickets_instances->get_tickets_instances_fields();
$columns = $tickets_instances->get_columns();
?>
<div class="wrap tc_wrap">