Null Coalescing, Spaceship and Other Operators

PHP 7.0 added the null coalescing operator ?? (returns the left side if it exists and isn't null, without notices) and the spaceship operator <=> for three-way comparison (ideal for usort). PHP 7.4 added ??=. These replace verbose isset() ternaries and comparison functions common in PHP 5 code.

<?php
// PHP 5 style
$page = isset($_GET['page']) ? (int) $_GET['page'] : 1;
// PHP 7
$page = (int) ($_GET['page'] ?? 1);

usort($products, function ($a, $b) {
    return [$a['category'], $b['price']] <=> [$b['category'], $a['price']];  // category asc, price desc
});

$config['timeout'] ??= 30;   // PHP 7.4

Common pitfalls

• ?? only checks null/undefined — an empty string or 0 is returned as-is.
• Using ?: (Elvis) when you meant ??; ?: treats falsy values like 0 as missing.
• Comparing arrays with <=> element by element without realizing order matters.

Key points

• ?? replaces isset ternaries
• <=> simplifies sort callbacks
• ??= assigns defaults (7.4)

Further reading: PHP manual: comparison operators