Arithmetic & Assignment Operators
Operators let you perform math and assign values to variables.
Syntax
$x += 5; // same as $x = $x + 5;Arithmetic operators perform common math operations:
+addition,-subtraction*multiplication,/division%modulus (remainder),**exponentiation
Assignment operators
The basic assignment is =. Combined operators such as +=, -=, *= and .= update a variable in place.
Example
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When to use it
- Calculate the discounted subtotal using arithmetic operators before applying tax in a checkout flow.
- Use += to accumulate a running total inside a loop that processes order line items.
- Apply the modulo operator % to determine whether a loop iteration is even or odd for zebra-striping table rows.
More examples
Arithmetic operators
The five arithmetic operators perform the core math needed in pricing, percentage, and division calculations.
<?php
$price = 100;
$discount = 15;
$subtotal = $price - $discount; // 85
$tax = $subtotal * 0.1; // 8.5
$total = $subtotal + $tax; // 93.5
$share = $total / 2; // 46.75
$leftover = 100 % 3; // 1
echo number_format($total, 2);Assignment operators
+= and its siblings (-=, *=, /=, %=) shorten the common read-modify-write pattern inside loops.
<?php
$total = 0;
$items = [10, 25, 8, 42];
foreach ($items as $item) {
$total += $item; // equivalent to $total = $total + $item
}
echo $total; // 85Modulo for even/odd rows
The modulo operator returns the remainder of division, making it the classic tool for alternating row classes.
<?php
$rows = ['Alice', 'Bob', 'Carol', 'Dave'];
foreach ($rows as $i => $name) {
$class = ($i % 2 === 0) ? 'even' : 'odd';
echo "<tr class=\"$class\"><td>$name</td></tr>\n";
}
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