switch and match

One value, many possibilities

When you compare the same variable against a list of values, a long if / elseif chain repeats itself:

<?php
if ($status === 'pending') {
    $label = 'Waiting for payment';
} elseif ($status === 'paid') {
    $label = 'Preparing your order';
} elseif ($status === 'shipped') {
    $label = 'On its way';
} // ...and so on

PHP has two constructs for this situation: the classic switch statement and the newer match expression from PHP 8.

switch

A switch takes one value and jumps to the case that equals it. Each case ends with break, which leaves the switch. default runs when no case matches:

<?php
$status = "shipped";

switch ($status) {
    case "pending":
        echo "Waiting for payment\n";
        break;
    case "paid":
        echo "Preparing your order\n";
        break;
    case "shipped":
        echo "On its way\n";
        break;
    default:
        echo "Unknown status\n";
}

On its way

Fall-through

The break is easy to forget, and forgetting it changes the meaning. Without break, PHP keeps going into the next case, whatever its label:

<?php
$status = "paid";

switch ($status) {
    case "paid":
        echo "Preparing your order\n";
    case "shipped":
        echo "On its way\n";
        break;
    default:
        echo "Unknown status\n";
}

Preparing your order
On its way

That is usually a bug. Sometimes it is used on purpose to give several values the same code, by stacking empty cases:

<?php
$day = "Sun";

switch ($day) {
    case "Sat":
    case "Sun":
        echo "Weekend: open 10 to 4\n";
        break;
    default:
        echo "Weekday: open 9 to 6\n";
}

Weekend: open 10 to 4

switch compares loosely

switch uses ==, so the type juggling described in Comparisons, == versus === and type juggling applies:

<?php
$quantity = "1";

switch ($quantity) {
    case 1:
        echo "Matched the integer 1\n";
        break;
    default:
        echo "No match\n";
}

Matched the integer 1

match

PHP 8 introduced match, which fixes switch's three weak spots. It is an expression, so it returns a value; it compares with ===; and it never falls through.

<?php
$status = "shipped";

$label = match ($status) {
    "pending" => "Waiting for payment",
    "paid" => "Preparing your order",
    "shipped" => "On its way",
    "delivered" => "Delivered",
    default => "Unknown status",
};

echo $label . "\n";

On its way

Each arm is value => result, separated by commas. Several values can share an arm:

<?php
function openingHours(string $day): string
{
    return match ($day) {
        "Sat", "Sun" => "10 to 4",
        "Mon", "Tue", "Wed", "Thu", "Fri" => "9 to 6",
    };
}

echo openingHours("Sun") . "\n";
echo openingHours("Wed") . "\n";

10 to 4
9 to 6

No match is an error

match must produce a value. If nothing matches and there is no default arm, it throws an UnhandledMatchError. That sounds harsh, but it turns a silent bug (an unexpected value slipping through) into an error you notice:

<?php
$day = "Holiday";

echo match ($day) {
    "Sat", "Sun" => "Weekend",
    "Mon", "Tue", "Wed", "Thu", "Fri" => "Weekday",
};

Fatal error: Uncaught UnhandledMatchError: Unhandled match case 'Holiday' in /path/to/script.php:4
Stack trace:
#0 {main}
  thrown in /path/to/script.php on line 4

Strict comparison

Because match uses ===, the string "1" does not match the integer 1:

<?php
$quantity = "1";

echo match ($quantity) {
    1 => "integer one",
    "1" => "string one",
} . "\n";

string one

match(true) for ranges

match compares values, but you can test a list of conditions by matching against true. The first arm whose condition is true wins:

<?php
function band(int $score): string
{
    return match (true) {
        $score >= 90 => "A",
        $score >= 75 => "B",
        $score >= 50 => "C",
        default => "Fail",
    };
}

echo band(82) . " " . band(91) . " " . band(30) . "\n";

B A Fail

Which one to use

Prefer match when you are turning one value into another, which covers most cases: labels, prices per plan, CSS classes per status. Use switch (or plain if) when each case needs several statements, because a match arm holds a single expression. For a fixed set of statuses, enums combine nicely with match.

A useful test: if you are about to write $label = ... in every case of a switch, rewrite it as one match assigned to $label. The result is shorter, every arm is visibly a value, and an unexpected input can no longer slip through unnoticed, because it either reaches default or throws an error you will see straight away.

Common mistakes

• Forgetting break in a switch, so the next case runs too.
• Expecting switch to compare strictly. It uses ==.
• Leaving out default in a match when unexpected values are possible, which throws an error.
• Trying to put several statements in a match arm. Call a function from the arm instead.

Exercise

Write a function planPrice(string $plan): int with match that returns 0 for "free", 499 for "pro" and 1999 for "team", and throws an error for anything else. Then print the price of "pro" and "team".

<?php
function planPrice(string $plan): int
{
    return match ($plan) {
        "free" => 0,
        "pro" => 499,
        "team" => 1999,
    };
}

echo planPrice("pro") . "\n";
echo planPrice("team") . "\n";

499
1999