Learning PHP - Need Help with Forms (Checkboxes)

Kenneth Pardue wrote:

> I'm trying to make a simple form submission script. One of the options
> I'm trying to include are checkboxes for a few options. However, if one
> of the checkboxes are left unchecked, the PHP doesn't recognize it as
> valid.
>
> Here's what I have:
>
> In my form:
> <input type='checkbox' name='checkbox[]' value='Option 1'>
> <input type='checkbox' name='checkbox[]' value='Option 2'>
> <input type='checkbox' name='checkbox[]' value='Option 3'>
>
> In the PHP processing script:
> $strengths[] = $_REQUEST['strengths[]'];
>
> echo "<p>" . $strengths[0] . $strengths[1] . $strengths[2] . "</p>"
>
> Any thoughts on what I'm doing wrong?
>
> Thanks,
> Kenneth
>

Just to provide complete information, the error message that I'm getting is:
Notice: Undefined index: checkbox[]