Do checkbox inputs only post data if they're checked?

Question

Is it standard behaviour for browsers to only send the checkbox input value data if it is checked upon form submission?

And if no value data is supplied, is the defa

Answer 1

None of the above answers satisfied me. I found the best solution is to include a hidden input before each checkbox input with the same name.

Then on the server side, using a little algorithm you can get something more like HTML should provide.

function checkboxHack(array $checkbox_input): array
{
    $foo = [];
    foreach($checkbox_input as $value) {
        if($value === 'on') {
            array_pop($foo);
        }
        $foo[] = $value;
    }
    return $foo;
}

This will be the raw input

array (
    0 => 'off',
    1 => 'on',
    2 => 'off',
    3 => 'off',
    4 => 'on',
    5 => 'off',
    6 => 'on',
),

And the function will return

array (
    0 => 'on',
    1 => 'off',
    2 => 'on',
    3 => 'on',
)