Making decisions: if, else, switch and match

Programs become useful when they react to data: show a discount to members, an error for invalid input, or a different greeting in the morning. Conditionals make that possible.

if, elseif and else

<?php

$hour = (int) date('G'); // 0 to 23

if ($hour < 12) {
    echo 'Good morning';
} elseif ($hour < 18) {
    echo 'Good afternoon';
} else {
    echo 'Good evening';
}

PHP checks each condition in order and runs the first block whose condition is true. The else block runs if none matched. Both elseif and else are optional.

Truthy and falsy values

A condition does not have to be a boolean. PHP converts the value, and these all count as false:

Everything else is true, including 'false', ' ' (a space) and '0.0'.

<?php

$items = [];

if ($items) {
    echo 'You have items';
} else {
    echo 'Your basket is empty';
}

Combining conditions

<?php

$age = 16;
$hasConsent = true;

if ($age >= 18 || ($age >= 13 && $hasConsent)) {
    echo 'Account can be created';
}

Brackets make mixed && and || conditions readable, even where precedence would give the same result.

Avoid deep nesting with early returns

Nested if blocks quickly become hard to follow. Inside a function you can check failure cases first and return early:

<?php

function shippingCost(float $total, string $country): float
{
    if ($total <= 0) {
        return 0.0;
    }

    if ($country !== 'GB') {
        return 15.0;
    }

    return $total >= 50 ? 0.0 : 4.99;
}

echo shippingCost(60, 'GB'); // 0
echo shippingCost(20, 'GB'); // 4.99

Each rule is visible at a glance. You will learn functions properly in a later lesson.

switch

switch compares one value against several cases:

<?php

$day = 'sat';

switch ($day) {
    case 'sat':
    case 'sun':
        echo 'Weekend';
        break;
    case 'fri':
        echo 'Almost there';
        break;
    default:
        echo 'Weekday';
}

Without break, execution "falls through" into the next case. That is useful for grouping cases (sat and sun above) and a classic source of bugs when forgotten. switch also uses loose == comparison.

match: the modern alternative

PHP 8 added match, an expression that returns a value:

<?php

$status = 404;

$message = match ($status) {
    200, 201 => 'Success',
    301, 302 => 'Redirect',
    404 => 'Not found',
    500 => 'Server error',
    default => 'Unknown status',
};

echo $message; // Not found

Why match is usually better than switch:

• It returns a value, so you assign the result directly.
• It uses strict === comparison.
• There is no fall-through and no break to forget.
• If no arm matches and there is no default, it throws an UnhandledMatchError instead of silently doing nothing.

match (true) lets you match on conditions:

<?php

$score = 82;

$grade = match (true) {
    $score >= 90 => 'A',
    $score >= 75 => 'B',
    $score >= 60 => 'C',
    default => 'Needs work',
};

echo $grade; // B

Summary

• if, elseif and else run the first matching block.
• 0, '0', '', [], null and false are falsy; check explicitly when 0 is valid input.
• Early returns keep logic flat and readable.
• switch falls through without break and compares loosely.
• Prefer match for mapping values: it is strict, returns a value and fails loudly.