Exclude post on loop by multiple meta key value

Question

I need to exclude the loop two post with different values in your meta key (the same). I investigating got this code that works fine if I enter only one value in value =>. But if I want to enter two values it gives me error.

$args = array(
    'cat'           => 1,
    'meta_query'    => array(
        'relation'  => 'OR',
        array(
            'key'     => 'Caja',
            'compare' => 'NOT EXISTS'
        ),
        array(
            'key'     => 'Caja',
            'value'   => array('UNO','DOS'), // Here I return an error php: Warning: trim() expects parameter 1 to be string, array given
            'compare' => '!='
        ),
    ),
);

I used this post as a reference.

Any ideas?

Answer 1

Straight from the codex

value (string|array) - Custom field value. It can be an array only when compare is 'IN', 'NOT IN', 'BETWEEN', or 'NOT BETWEEN'.

SOLUTION

Change compare' => '!=' to compare' => 'NOT IN'