Match expression - An alternative to switch statement in PHP 8
The switch statement in PHP is great when you want check condition on the same expression without incorporating many if statements altogether.
Good ol’ switch statement
This is a basic if-else comparison on a same expression.
<?php
if ($i == 'apple') {
echo 'i is apple';
} elseif ($i == 'cake') {
echo 'i is cake';
} else {
echo 'i is pizza';
}
And this how the equivalent switch statement of previous example would look like
<?php
switch ($i) {
case 'apple':
echo 'i is apple';
break;
case 'cake':
echo 'i is cake';
break;
default:
echo 'i is pizza';
}
Now, this looks fine in comparison to the if-else statement as you don’t have to explicitly compare the expression explicitly. But it’s still sort of verbose and PHP 8 wants to change that using “Match expression”.
Match expression
An alternative for switch statement called “Match expression” has been accepted in this RFC.
From the RFC…
The RFC proposes adding a new match expression that is similar to switch but with safer semantics and the ability to return values.
So, if we want to rewrite the previous example using match expression, it would look like so.
<?php
echo match ($i) {
'apple' => 'i is apple',
'cake' => 'i is cake',
default => 'i is pizza',
};
As you can see, the match expression has made the code quite compact and concise as opposed to switch statement. Apart from this visual benefit, match expression has many other benefits over switch statement.
Strict comparison
As opposed to switch statement, the match expression uses strict comparison (===). So, following example with switch statement…
switch ('foo') {
case 0:
$result = "Oh no!\n";
break;
case 'foo':
$result = "This is what I expected\n";
break;
}
echo $result;
//> Oh no!
…Would return from case 0 as it would compare 'foo' == 0. The similar example with match expression would work just as expected.
echo match ('foo') {
0 => "Oh no!\n",
'foo' => "This is what I expected\n",
};
//> This is what I expected
No issue of forgetting ‘break’
The switch fallthrough has been a large source of bugs in many languages. Each case must explicitly break out of the switch statement or the execution will continue into the next case even if the condition is not met.
switch ($pressedKey) {
case Key::RETURN_:
save();
// Oops, forgot the break
case Key::DELETE:
delete();
break;
}
The match expression resolves this problem by adding an implicit break after every arm.
match ($pressedKey) {
Key::RETURN_ => save(),
Key::DELETE => delete(),
};
Multiple comma-separated conditions
Multiple conditions can be comma-separated to execute the same block of code.
echo match ($x) {
1, 2 => 'Same for 1 and 2',
3, 4 => 'Same for 3 and 4',
};
No need to return value from each cases
Using match expression, it’s no longer needed to return values from each cases. So, where you’d need to store a value in each case like so…
switch (1) {
case 0:
$result = 'Foo';
break;
case 1:
$result = 'Bar';
break;
case 2:
$result = 'Baz';
break;
}
…Would get simplified with match expression.
echo match (1) {
0 => 'Foo',
1 => 'Bar',
2 => 'Baz',
};
//> Bar
Caveat
There is one caveat with match caveat right now and that, as you may probably guessed, is it would only be used with one-liner expressions. So, the cases when you’d want to use multiple line case blocks, you’d need to stick to the switch statement only.
You can learn more about the feature here.
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