Updating post meta for custom post types

I really like your clean class structure 🙂 But I have a suggestion that might fix things (based on my experience with nonces and meta boxes from a plug-in I built last weekend):

Don’t try to create the nonce field manually. You currently have:

$nonce = wp_create_nonce( plugin_basename( __FILE__ ) );

...

<input type="hidden" name="argus_edit_visitor" id="argus_edit_visitor" value="{$nonce}" />

The standard way to create this field is using WordPress’ wp_nonce_field() function. It will add the hidden field for you:

wp_nonce_field( __FILE__, 'argus_edit_visitor' );

Verifying the nonce

You’re verifying against the wrong string. In your code, you created the nonce with __FILE__ but you verify with the string argus_edit_vistor. You have:

if ( empty($_POST)
    OR !isset($_POST['argus_edit_visitor'])
    OR !wp_verify_nonce( $_POST['argus_edit_visitor'], 'argus_edit_visitor' ) )
    {
        echo "Erm. Why?";
        return $post->ID;
    }

You should have:

if ( empty($_POST)
    OR !isset($_POST['argus_edit_visitor'])
    OR !wp_verify_nonce( $_POST['argus_edit_visitor'], __FILE__ ) )
    {
        echo "Erm. Why?";
        return $post->ID;
    }

I usually use plugin_basename(__FILE__) when creating nonces. But you shouldn’t run into problems doing it your way so long as the nonce creation and nonce verification happens in the same file.