Querying users by meta value and getting a strange answer

Question

Here is my case:

I am trying to get all users with some value related to a specific meta key. In other words, I don't want to select users that have nothing on that meta key (mps_finalDate).

So here is my code:

$users = get_users(array(
 'meta_key'     => 'mps_finalDate',
 'meta_value'   => '',
 'meta_compare' => '!=',
 ));

Which works the same as

$users = get_users(array(
  'meta_key'     => 'mps_finalDate',
  ));

But the problem is: this code is selecting users that once had some value on this meta field, even if now they have nothing on it. It seems that the update_user_meta( $user_id, 'mps_finalDate', trim( $_POST['mps_finalDate'] ) ); I am using in my code is not deleting the previous value on the db, thus causing this issue.

In conclusion: the above code is not selecting a user that never had a value on the meta key field mps_finalDate(which is desired), but it is selecting a user that once had a value on it, even if now this value is "".

Any help?

Answer 1

It looks like you're using a custom meta field but searching default meta attributes.

https://codex.wordpress.org/Class_Reference/WP_User_Query

WP_User_Query might be a more robust solution.

So it would look like something like :

$args = array(
    'meta_query' => array(
        'relation' => 'AND',
        array(
            array(
                'key'     => 'mps_finaldate',
                'value'   => '',
                'compare' => '!='
            ),
            array(
                'key'     => 'mps_finaldate',
                'value'   => null,

                'compare' => '!='
            )
        )
    )
 );
$user_query = new WP_User_Query( $args );

EDIT:

WP_User_Query is a wrapper for the get_users function you were using but it, as a wrapper, also is going to do the work of the get_userdata function

This is great and detrimental for 2 reasons (each)

Great: it can be hooked (someone edit me) Great: code longevity is sustained because it is core api use

Detrimental: anyone and everyone's plugins can also hook Detrimental: anyone and everyone's plugins can also hook

I'd go the route of using the wp_user_query class if only because the arguments are structured and documented well (but I'll stay for the longevity benefit of the approach being wp_core api)

your mileage may vary