Given that you've designed your form something like this:
<input type="checkbox" name="things[1]" value="Football">
<input type="checkbox" name="things[2]" value="Tennis">
...you could try this code:
<?php
foreach ($things as $key => $value)
{
print "$key: $value<br>\n";
}
?>
Check out whether you need to use stripslashes() on $value, since it is probably printed directly from your GET/POST data. It depends on the PHP configuration.