Operators
PHP Manual

Arithmetic Operators

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

Arithmetic Operators
Example Name Result
+$a Identity Conversion of $a to int or float as appropriate.
-$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 Modulo Remainder of $a divided by $b.
$a ** $b Exponentiation Result of raising $a to the $b'th power.

The division operator / returns a float value unless the two operands are int (or numeric strings which are type juggled to int) and the numerator is a multiple of the divisor, in which case an integer value will be returned. For integer division, see intdiv.

Operands of modulo are converted to int before processing. For floating-point modulo, see fmod.

The result of the modulo 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

var_dump(5 % 3);
var_dump(5 % -3);
var_dump(-5 % 3);
var_dump(-5 % -3);

?>

The above example will output:

int(2)
int(2)
int(-2)
int(-2)

See Also