When processing form data in PHP, what considerations should be made regarding the relationship between input fields and checkboxes?

When processing form data in PHP, it is important to consider the relationship between input fields and checkboxes. If a checkbox is unchecked, its corresponding value may not be sent in the form data. To ensure that the checkbox value is always included in the form data, you can use a hidden input field with the same name as the checkbox. This hidden input field will have a default value that represents the unchecked state, and it will be submitted along with the form data.

<input type="checkbox" name="my_checkbox" value="1">
<input type="hidden" name="my_checkbox" value="0">