Remember basic arithmetic from school? These work just like those.
| 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:
  
Example #1 The Modulo Operator
<?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)