If you want to avoid a million `isset()`/`empty()` checks, a possible approach would be to set up some defaults that you `array_merge` the `$comment_meta` array into.

```php
$defaults = array(
  'x1' => /* some default value */,
  'x2' => /* some default value */,
  'x3' => /* some default value */,
  // etc
);

$comment_meta = array_merge( $defaults, $comment_meta );
```