PHP Arithmetic Operators

Arithmetic operators perform mathematical operations on numbers. PHP supports all standard math operations plus some powerful extras like exponentiation. Let's master them all!

Arithmetic Operators Overview

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Addition (+)

Adds two numbers together:

<?php
$a = 10;
$b = 5;
$sum = $a + $b;
echo $sum;  // Output: 15

// Works with floats
$price1 = 19.99;
$price2 = 5.50;
$total = $price1 + $price2;
echo $total;  // Output: 25.49
?>

Subtraction (-)

Subtracts the second number from the first:

<?php
$a = 10;
$b = 5;
$difference = $a - $b;
echo $difference;  // Output: 5

// Can result in negative numbers
$result = 5 - 10;
echo $result;  // Output: -5
?>

Multiplication (*)

Multiplies two numbers:

<?php
$quantity = 5;
$price = 10.50;
$total = $quantity * $price;
echo $total;  // Output: 52.5

// Multiplying by zero
$result = 100 * 0;
echo $result;  // Output: 0
?>

Division (/)

Divides the first number by the second:

<?php
$total = 100;
$people = 4;
$perPerson = $total / $people;
echo $perPerson;  // Output: 25

// Division can result in floats
$result = 10 / 3;
echo $result;  // Output: 3.3333333333333
?>

Modulus (%)

Returns the remainder after division:

<?php
$number = 10;
$divisor = 3;
$remainder = $number % $divisor;
echo $remainder;  // Output: 1 (10 ÷ 3 = 3 remainder 1)

// Check if number is even or odd
$num = 7;
if ($num % 2 == 0) {
    echo "Even";
} else {
    echo "Odd";  // This executes
}
?>

Exponentiation (**)

Raises the first number to the power of the second (PHP 5.6+):

<?php
$base = 2;
$exponent = 3;
$result = $base ** $exponent;
echo $result;  // Output: 8 (2³ = 2 × 2 × 2)

// Calculate area of square
$side = 5;
$area = $side ** 2;
echo $area;  // Output: 25

// Fractional exponents (roots)
$number = 16;
$squareRoot = $number ** 0.5;
echo $squareRoot;  // Output: 4
?>

Negation (-)

Changes the sign of a number:

<?php
$positive = 10;
$negative = -$positive;
echo $negative;  // Output: -10

// Double negation returns original
$result = -(-10);
echo $result;  // Output: 10
?>

Operator Precedence

When multiple operators are used, PHP follows mathematical order of operations:

<?php
// Without parentheses
$result = 2 + 3 * 4;
echo $result;  // Output: 14 (not 20!)
// Calculation: 3 * 4 = 12, then 2 + 12 = 14

// With parentheses
$result = (2 + 3) * 4;
echo $result;  // Output: 20
// Calculation: 2 + 3 = 5, then 5 * 4 = 20

// Complex expression
$result = 2 ** 3 + 4 * 5;
echo $result;  // Output: 28
// Calculation: 2³ = 8, 4 * 5 = 20, 8 + 20 = 28
?>

Common Mistakes

<?php
$result = 10 / 0;  // ❌ Warning: Division by zero

// Always check first
$divisor = 0;
if ($divisor != 0) {
    $result = 10 / $divisor;
} else {
    echo "Cannot divide by zero";
}
?>

<?php
$result = 7 / 2;
echo $result;  // 3.5 (not 3!)

// For integer division, use intdiv() (PHP 7+)
$result = intdiv(7, 2);
echo $result;  // 3
?>

<?php
echo 10 % 3;   // 1
echo -10 % 3;  // -1 (takes sign of dividend)
echo 10 % -3;  // 1
?>

Summary

What's Next?

Now that you've mastered arithmetic operators, let's learn about Assignment Operators - shortcuts for updating variables with arithmetic operations!