Custom filter in admin edit custom post type responding with invalid post type?

Question

I am trying to add a filter to the admin edit screen for a custom post type called "trip" that I set up using Custom Post Types plugin. I'd like the filter to filter by the custom field added by ACF, "trip_status". Please see the image below for reference.

I am using the code below to set this up (modified from here), however every time I try to filter by the options in the dropdown I have created, I get a response "Invalid Post Type" from Wordpress.

/** Create the filter dropdown */
add_action( 'restrict_manage_posts', 
'atg_admin_trips_filter_restrict_manage_posts' );
function atg_admin_trips_filter_restrict_manage_posts($query){
  $type = 'post';
  if (isset($_GET['post_type'])) {
    $type = $_GET['post_type'];
  }
  if ('trip' == $type){
    $values = array(
        'Quality Check' => 'Quality Check', 
        'Pending Approval' => 'Pending Approval',
        'Pay Deposit' => 'Pay Deposit',
        'Deposit Paid' => 'Deposit Paid',
        'Collecting Names' => 'Collecting Names'
    );
    ?>
    <select name="tripstatus">
    <option value=""><?php _e('Filter By ', 'wose45436'); ?></option>
    <?php
        $current_v = isset($_GET['tripstatus'])?$_GET['tripstatus']:'';
        foreach ($values as $label => $value) {
            printf
                (
                    '<option value="%s"%s>%s</option>',
                    $value,
                    $value == $current_v? ' selected="selected"':'',
                    $label
                );
            }
    ?>
    </select>
    <?php
  }
}

/** Filter by post meta -> trip_status */
add_filter( 'pre_get_posts', 'atg_trips_posts_filter' );
function atg_trips_posts_filter( $query ){
  global $pagenow;
  $type = 'post';
  if (isset($_GET['post_type'])) {
    $type = $_GET['post_type'];
  }

  if( 'trip' == $type && is_admin() && $pagenow=='edit.php' && isset($_GET['tripstatus']) && $_GET['tripstatus'] != '') {

    $value = $_GET['tripstatus'];
    $query->query_vars['meta_key'] = 'trip_status';
    $query->query_vars['meta_value'] = $value;
    }
}

Any input anyone could offer as to why this is not working would be greatly appreciated. I now the issue is related to setting the query vars, but not sure what I'm doing wrong as I've verified the meta_key in the database is 'trip_status'.

This is the url output when I try to 'filter' the posts: http://localhost/BOOKINGSITE/wp-admin/edit.php?s=&post_status=all&post_type=trip&_wpnonce=f51f34525b&_wp_http_referer=%2FBOOKINGSITE%2Fwp-admin%2Fedit.php%3Fs%26post_status%3Dall%26post_type%3Dtrip%26action%3D-1%26m%3D0%26tripstatus%26filter_action%3DFilter%26paged%3D1%26action2%3D-1&action=-1&m=0&tripstatus=Quality+Check&filter_action=Filter&paged=1&action2=-1

Also, if anyone can provide insight into the difference between using parse_query versus pre_get_posts in this instance, or the difference between: 1- $query->query_vars['meta_key'] = 'trip_status'; 2- $query->set('meta_key', 'trip_status');

Answer 1

I am also get the issue same as you and finally I got the solution.

We have to add $query->is_main_query() in IF CONDITION.

if( 'trip' == $type && is_admin() && $pagenow=='edit.php' && isset($_GET['tripstatus']) && $_GET['tripstatus'] != '' && $query->is_main_query()) {

    $value = $_GET['tripstatus'];
    $query->query_vars['meta_key'] = 'trip_status';
    $query->query_vars['meta_value'] = $value;
    }

I hope it will help you to get the answer.