How can one verify the functionality of date_diff in PHP through the command line interface?

To verify the functionality of date_diff in PHP through the command line interface, you can create a PHP script that calculates the difference between two dates and then run it using the PHP command line interface. This will allow you to see the output directly in the terminal.

<?php
$date1 = new DateTime('2022-01-01');
$date2 = new DateTime('2022-01-10');
$interval = date_diff($date1, $date2);
echo $interval->format('%R%a days');
?>
```

Save the above code in a PHP file (e.g., date_diff_test.php) and run it using the PHP command line interface:

```
php date_diff_test.php