How can input-hidden fields be utilized to pass variables between PHP files?

To pass variables between PHP files, you can utilize input-hidden fields within a form. Simply include the variables you want to pass as hidden input fields in a form on the first PHP file, then submit the form to the second PHP file where you can access the variables using the $_POST array.

// First PHP file
<form action="second_file.php" method="post">
    <input type="hidden" name="variable1" value="value1">
    <input type="hidden" name="variable2" value="value2">
    <button type="submit">Submit</button>
</form>
```

```php
// Second PHP file (second_file.php)
$variable1 = $_POST['variable1'];
$variable2 = $_POST['variable2'];

// Now you can use $variable1 and $variable2 in this file