It is a bit unclear what you ask: php can only handle data on the server side. If you do not want some specific attribute of a dataset you read / write to / from a database to be modified, then just don’t do it. No one forces you to consider data you get, for example inside the $_POST values you get from a form submission.
However the checkboxes themselves are only presented at the client side. Only there users can modify the values. php does not have any control over that, since it is running on the server side.
What you could do is try to prevent changes to the checkboxes by means of javascript which can be used on the client side. This works by suppressing or better swallowing the click events raised by the user. But actually there is no need for that: html itself allows to declare a checkbox as disabled which prevents any modification.
If that is not what you looking for, maybe because of optical reasons, you might want to overwrite the value of the checkboxes on html level by adding a hidden field holding the same name and value. That way it is irrelevant what modifications users make.
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solved Prevent changing checkbox value [duplicate]