Wordpress WP_Query "NOT IN" not working

我有一个自定义字段Field Name: "participants"与Field Type: "User"。

我想在元查询中使用"NOT IN"，但它不工作。

$getUid = $_REQUEST['uid'];
$args = [
    'post_type' => 'polls',
    'post_status' => 'publish',
    'meta_query' => [
        'relation' => 'AND',
        [
            'key' => 'participants',
            'value' => [$getUid],
            'compare' => "NOT IN"
        ]
    ]
];
$the_query = new WP_Query($args);
return $the_query;

使用此代码并确保在$REQUEST['uid']中获得值

   $getUid = $_REQUEST['uid'];
    $meta_query_args = array(
        'relation' => 'AND', // Optional, defaults to "AND"
        array(
            'post_type' => 'polls',
        'post_status' => 'publish',
            'key' => 'participants',
                'value' => [$getUid],
                'compare' => "NOT IN"
        )
    );
    $meta_query = new WP_Meta_Query( $meta_query_args );