I discovered by accident that PHP allows you to format the iterator in a for loop with sprintf(), as long as the result of sprintf() can evaluate to the same numeric type as your step value. As a contrived example, consider the following loop used to build out the options in a "months of the year" select list:

$month = '<select name="month">';
for ($i = 1; $i < 13; $i++) {
    $month .= '<option value="' . sprintf('%02d', $i) . '">' . sprintf('%02d', $i);
}
$month .= '</select>';

The same loop can be written this way:

$month = '<select name="month">';
for ($i = sprintf('%02d', 1); $i < sprintf('%02d', 13); $i = sprintf('%02d', ++$i)) {
    $month .= '<option value="' . $i . '">' . $i;
}
$month .= '</select>';

That is, the formatting of $i into a two-digit zero-padded integer is being done inside of the control block itself, instead of as a separate instruction inside the loop.

In this specific example, there's no benefit (and in fact there is some detri...