Control Flow and match

Branches and loops

PHP has the familiar if/elseif/else, while, do-while, for and foreach, the main way to iterate arrays and other iterables (foreach ($orders as $id => $order)). match (PHP 8.0) is an expression that returns a value, compares with strict identity (===), has no fall-through, can list several values per arm and throws an UnhandledMatchError if nothing matches and there is no default. That makes it safer than switch, which compares loosely and falls through without break. foreach by reference (foreach ($items as &$item)) modifies the array in place but leaves $item referencing the last element afterwards, a classic bug, so unset($item) after such loops or avoid references entirely. break and continue accept a number to exit nested loops (break 2). Prefer early returns and small functions over deeply nested conditions.

match versus switch

match returns a value with strict comparison and no fall-through; switch compares loosely and falls through.

match, foreach and early returns

match maps statuses to labels with strict comparison.

<?php
declare(strict_types=1);

function statusLabel(string $status): string
{
    return match ($status) {
        'placed', 'paid' => 'In progress',
        'shipped'        => 'On the way',
        'delivered'      => 'Delivered',
        'cancelled'      => 'Cancelled',
        default          => throw new InvalidArgumentException("Unknown status {$status}"),
    };
}

$orders = ['o-1' => 'paid', 'o-2' => 'shipped', 'o-3' => 'cancelled'];

foreach ($orders as $id => $status) {
    if ($status === 'cancelled') {
        continue;                       // skip early
    }
    echo $id, ': ', statusLabel($status), PHP_EOL;
}

Reference loops leave a dangling reference

After foreach ($rows as &$row), $row still points at the last element. A later foreach ($rows as $row) overwrites that last element on every iteration. Call unset($row) right after the reference loop.

त्वरित जाँच: Which is true about match compared with switch?

• match compares loosely like ==
• match requires break statements
• match uses strict comparison, returns a value and does not fall through
• match cannot have a default arm