Out of all operators in programming, it is the modulo operator that goes under the radar most. Perhaps this is due to a lack of need or even an understanding of how it works and when to use it.

In the simplest terms, modulo operator is the remainder from a division of one number by another. Compare this to a simple division which is the times the number goes into the other.

### Examples

Here are some examples in PHP

echo (20 % 12);//8

The answer is 8 because 12 goes into 20 once and 8 is left over.

echo (40 % 12);//4

12 goes into 40 three times (36) and 4 is the remainder.

Checking if a number is odd or even with the modulo operator:

if ($number % 2 == 0) { echo "Even"; } else { echo "Odd"; }

This works because 2 will always go into an even number and have 0 remaining.

Another great use for the modulo operator is running a loop and getting every tenth, hundred, thousandth etc;

for ($i = 1; $i <= 100000; $i++) { if ($i % 5000 == 0) { echo $i.'<br>'; } }

Outputs

5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 55000 60000 65000 70000 75000 80000 85000 90000 95000 100000

Whilst

for ($i = 1; $i <= 50000; $i++) { if ($i % 1500 == 0) { echo $i.'<br>'; } }

outputs

1500 3000 4500 6000 7500 9000 10500 12000 13500 15000 16500 18000 19500 21000 22500 24000 25500 27000 28500 30000 31500 33000 34500 36000 37500 39000 40500 42000 43500 45000 46500 48000 49500