PHP Manual: Arithmetic Operators

Arithmetic Operators

Remember basic arithmetic from school? These work just like those.

**Arithmetic Operators**
Example	Name	Result
-$a	Negation	Opposite of `$a`.
$a + $b	Addition	Sum of `$a` and `$b`.
$a - $b	Subtraction	Difference of `$a` and `$b`.
$a * $b	Multiplication	Product of `$a` and `$b`.
$a / $b	Division	Quotient of `$a` and `$b`.
$a % $b	Modulus	Remainder of `$a` divided by `$b`.

The division operator ("/") returns a float value unless the two operands are integers (or strings that get converted to integers) and the numbers are evenly divisible, in which case an integer value will be returned.

Operands of modulus are converted to integers (by stripping the decimal part) before processing.

The result of the modulus operator % has the same sign as the dividend — that is, the result of $a % $b will have the same sign as $a. For example:


<?php

echo (5 % 3)."\n";           // prints 2
echo (5 % -3)."\n";          // prints 2
echo (-5 % 3)."\n";          // prints -2
echo (-5 % -3)."\n";         // prints -2

?>

See also the manual page on Math functions.