title: Wordpress - CUSTOM FIELDS meta_query with several keys
body: <p>I have an issue with multiple meta_query keys in custom fields. So, in my wordpress I've added custom field with checkbox named 'Unavailable' so if the checkbox is clicked, the post won't appear.</p>
  <p>so, my meta_query looked like this:</p>
  <pre><code>'meta_query' =&gt; array(
                  array(
                      'key' =&gt; 'Unavailable',
                      'compare' =&gt; '=',
                      'value' =&gt; '0'
                  )
          )
  </code></pre>
  <p>and it worked fine. recently i've added second custom field called 'Invisible', also with checkbox property. Mainly, this field does the same as 'Unavailable' one, with one difference. The issues occures when I try to add an operator for those two keys. So if unavailable or invisible is checked, do something.</p>
  <p>I tried, but it doesn't work:</p>
  <pre><code>'meta_query' =&gt; array(
                 'relation' =&gt; 'OR'
                  array(
                      'key' =&gt; 'Unavailable',
                      'compare' =&gt; '=',
                      'value' =&gt; '0'
                  ),
                  array(
                      'key' =&gt; 'Invisible',
                      'compare' =&gt; '=',
                      'value' =&gt; '0'
                  ),
          )
  </code></pre>