Learn PHPin 24 Hours

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…)

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