10. PHP Operators

What you will learn

• Arithmetic, assignment, comparison, and logical operators
• The string, null coalescing, and ternary operators
• The spaceship operator
• Operator precedence

Arithmetic and assignment

<?php
$x = 10;
$x += 5;
$x *= 2;
$x -= 4;
$x++;

$text = "Hello";
$text .= " World";

echo $x . " | " . $text;

The .= operator adds text to the end of a string.

Comparison operators

<?php
var_dump(5 === "5");
var_dump(5 !== "5");
var_dump(3 <=> 7);
var_dump(7 <=> 7);
var_dump(9 <=> 7);

bool(false)
bool(true)
int(-1)
int(0)
int(1)

The spaceship operator <=> is handy for sorting.

Logical operators

<?php
$age = 20;
$has_ticket = false;

echo "AND: " . var_export($age >= 18 && $has_ticket, true) . "<br>";
echo "OR: " . var_export($age >= 18 || $has_ticket, true) . "<br>";
echo "NOT: " . var_export(!$has_ticket, true);

PHP also has the words and and or, but they have lower precedence and cause surprises. Stick with && and ||.

Ternary and null coalescing

<?php
$age = 16;
echo ($age >= 18 ? "adult" : "minor") . "<br>";

$user = null;
echo ($user ?? "Guest") . "<br>";

$settings = ["theme" => "dark"];
echo $settings["theme"] ?? "light";
echo " / ";
echo $settings["font"] ?? "default font";

The ?? operator returns the left side if it exists and is not null, otherwise the right side. It does not raise a warning for a missing array key, which makes it ideal for reading form data and settings.

Precedence

PHP follows the usual order: multiplication and division come before addition and subtraction. Use brackets to make your meaning clear.

<?php
echo 2 + 3 * 4;
echo " | ";
echo (2 + 3) * 4;

Joining text and numbers

PHP 8 treats + as arithmetic only and . as joining. Mixing them without brackets can give surprising results, because + and - bind tighter than .. Wrap calculations in brackets when you build text.

<?php
echo "Total: " . (5 + 6);

Common mistakes

• Writing = instead of === in a condition.
• Using == and being surprised by conversion.
• Using + to join text.
• Forgetting brackets around a calculation inside joined text.
• Using and and or instead of && and ||.

<?php
$input = null;
echo $input ?? "Anonymous";

Summary

• Use === and !== for comparisons, and &&, ||, ! for logic.
• . joins text, and ?? supplies fallbacks.
• Use brackets to make precedence clear.