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 integers (or strings that get converted to integers) and the numbers are evenly divisible, 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

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