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.
$a ** $b Exponentiation Result of raising $a to the $b'th power. Introduced in PHP 5.6.

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

?>

See also the manual page on Math functions.

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r dot shipelov at tradesoft dot ru
1 year ago
Regarding the operation of division with remainder (%) - it differs from the one accepted in mathematics, since it is looking for "refusal" and not "remainder" - a feature of the idiv implementation in 8086
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