PHP Operators

PHP Operators: Arithmetic, Comparison, Logical, & Modern Operators

Operators perform operations on variables and values. PHP includes arithmetic, assignment, comparison, logical, bitwise, string concatenation, and modern operators like Null Coalescing (??) and Spaceship (<=>).

Categories of Operators

1. Arithmetic: +, -, *, /, % (Modulo), ** (Exponentiation)
2. Comparison: ==, === (Strict), !=, !==, <, >, <=, >=, <=> (Spaceship)
3. Logical: && (AND), || (OR), ! (NOT)
4. Assignment: =, +=, -=, *=, /=, .=
5. Null Coalescing: $val ?? $default (Returns $val if set and not null, otherwise $default)

Spaceship Operator (<=>) & Null Coalescing (??)

flowchart TD
    A["Evaluation Operator"] --> B{"Choose Operator"}
    B -- Spaceship ($a <=> $b) --> C["Returns -1 if $a < $b, 0 if $a == $b, 1 if $a > $b"]
    B -- Null Coalescing ($a ?? $b) --> D["Returns $a if set and non-null, else $b"]
    B -- Strict Equality ($a === $b) --> E["Compares both value and type"]

Practical Code Example

<?php
declare(strict_types=1);

// 1. Strict vs Loose Comparison
$ageString = "25";
$ageInt = 25;

echo "Loose Equality (==): " . ($ageString == $ageInt ? "True" : "False") . "
";   // True
echo "Strict Equality (===): " . ($ageString === $ageInt ? "True" : "False") . "
"; // False

// 2. Spaceship Operator (<=>) for Sorting Arrays
$numbers = [10, 5, 20, 15];
usort($numbers, fn($a, $b) => $a <=> $b); // Ascending sort: [5, 10, 15, 20]
echo "Sorted Numbers: " . implode(", ", $numbers) . "
";

// 3. Null Coalescing Operator (??) & Assignment (??=)
$requestData = ['username' => 'maksudur'];
$currentUser = $requestData['username'] ?? 'Guest';
$theme = $requestData['theme'] ??= 'dark_mode'; // Assigns 'dark_mode' if 'theme' is unset

echo "Current User: $currentUser | Selected Theme: $theme
";

Best Practices

• Always Use Strict Comparison === and !==: Prevents unexpected bugs caused by implicit PHP loose type coercions (e.g. "0" == false evaluates to true!).
• Use Null Coalescing Operator ?? over isset() Ternary: Use $val ?? 'default' instead of isset($val) ? $val : 'default'.
• Use Spaceship Operator <=> in Callback Comparison Functions: Simplifies custom array sorting callbacks in usort().

Self-Check Challenge

Write a line of code using the null coalescing operator ?? that assigns $userRole to $_GET['role'] if it exists, or 'subscriber' if it is missing or null!