PHP also provides an operator that might be less familiar: modulo (%). The modulo operator returns the remainder after the left operand is divided by the right operand.

echo 7 % 3; // Prints: 1

In the code above, 7 % 3 returns 1. Why? We’re trying to fit 3 into 7 as many times as we can. 3 fits into 7 at most twice. What’s left over—the remainder—is 1, since 7 minus 6 is 1.

The modulo operator will convert its operands to integers before performing the operation. This means 7.9 % 3.8 will perform the same calculation as 7 % 3—both operations will return 1.

Let’s look at another example of the modulo operator in action:

$num_cookies = 27;
$cookies_per_serving = 4;
$leftover_cookies = $num_cookies % $cookies_per_serving;
echo $leftover_cookies; // Prints: 3

Let’s practice using modulo!