Checkbox in an array

Okay, Try this:
in the part of the script which goes after form submitting put this:

$message = NULL;
if (empty($_POST['name_of_var'])) {
$variable_1 = FALSE;
$message .= '<p>Field Nr 1. is empty!</p>';
} else {
$variable_1 = $_POST['name_of_var'];
}

You can put as many of them as necessary. After that you gotta do simple check:

if ($variable_1 && $variable_2 && $variable_3 etc...)
{
put your script which process form values here
}
else {
print $message;
}

zbrdlowski, the OP has reached a solution for the problem already. You can stop now.

Okay... I just realized, there are many ways how to get the same result as he want...