Comparing a field with several values at once with meta_query

Question

The parameter ‘meta_query’ is an array, so you can add multiple meta keys. In the doc, below the section “Example: Multiple Meta Entries – Multi dimensional array”, you can find an example where the relation is set to ‘OR’:

$query_args = array( 'meta_query' => array(
'relation' => 'OR',
array(
    'key' => 'foo_key',
    // 'value' => 'foo',
    // 'compare' => 'LIKE',
),
array(
    'key' => 'bar_key',
),
) );
[...]

The result query will then be:

'join' => string ' INNER JOIN wp_postmeta ON wp_posts.ID = wp_postmeta.post_id' (length=60)
'where' => string ' AND (wp_postmeta.meta_key = 'foo_key' OR wp_postmeta.meta_key = 'bar_key' )'
(length=75)

If you want to check for multiple values with the same key, you can use an array and use ‘IN’ to compare:

array(
    'key' => 'foo_key',
    'value' => array('foo', 'bar'),
    'compare' => 'IN'
),