PHP Modulo Tutorial

Written by Aaron

Topics: PHP Scripting

Modulo math is very important to many fields of study. For example, we perform modulo 12 arithmatic any time we read an analog clock.

According to Wikipedia:

In mathematics, modular arithmetic (sometimes called clock arithmetic) is a system of arithmetic for integers, where numbers “wrap around” after they reach a certain value—the modulus.

PHP modulo arithmatic isn’t hard but it’s something you need in your set of tools as a PHP programmer.  You might use it to check if a number is odd or even, to create a series of numbers that repeats (0, 1, 2, 0, 1, 2…), to find the remainder from a division problem, etc.

PHP uses the percent sign (%) to perform modulo arithmatic.  For example:

<?php
echo 4 % 12 . "\n";
echo 12 % 12 . "\n";
echo 13 % 12 . "\n";
echo 13.21 % 12.1 . "\n";
echo -13 % 12 . "\n";
?>

will result in:

4
0
1
1
-1

Note that:

  • Decimal values are stripped down to integers (13.6 becomes 13 for example)
  • Negative values are taken into account (be careful not to forget…)

Back to Learn PHP in 24 Hours for more fun :-)

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