how do I get all checkbox variables even if not checked from HTML to PHP?

Question

I noticed that PHP seems to return only values of checked checkboxes. I would like to see a list of checkboxes, not just values of checked checkboxes. Is there a way to detect variables of unchecked boxes?

I asked because I want to be able to update settings. For example, I have a few options that are already checked but if an user decides to uncheck an option, I need to know that unchecked value so I can update the option to be disabled.

Answer 1

I just ran into this problem myself. I solved it by adding a duplicate hidden field with the same name. When the browser sends this information, the second field overrides the first (so ensure that the hidden field comes first).

<input type="hidden" name="foo" value="">
<input type="checkbox" name="foo" value="bar">

If the checkbox is not checked you get:

$_REQUEST[ 'foo' ] == ""

If the checkbox is checked you get:

$_REQUEST[ 'foo' ] == "bar"