Expressions: Match
The match expression branches evaluation based on an identity check of a value.
$variable = match subject {
condition => expression,
first_condition, second_condition => expression,
};
Example
function get_emoji(string $food): string {
match $food {
'pizza' => '🍕',
'burger' => '🍔',
'hotdog' => '🌭',
'taco' => '🌮',
'burrito' => '🌯',
default => '🤔',
}
}
function example(): void {
$emoji = get_emoji('pizza');
IO\write_line($emoji); // 🍕
}
default condition
The default condition is used to match any value that does not match any other condition.
Multiple conditions
Multiple conditions can be provided for a single expression by separating them with a comma.
$variable = match subject {
condition, another_condition => expression,
};
Non exhaustive match
If a match expression is not exhaustive, meaning that it does not have a default condition and does not cover all possible values, the compiler will error.
Example, the following code will result in a compiler error:
enum Color {
case Red;
case Green;
case Blue;
}
function get_color_name(Color $color): string {
// This match expression is not exhaustive, because it does not cover all possible values of Color.
match $color {
Color::Red => 'Red',
Color::Green => 'Green',
}
}
Short Match
A short match expression is a match expression that has a subject of value true.
$variable = match {
condition => expression,
first_condition, second_condition => expression,
};
Example
$result = match {
$a == $b => 'a is equal to b',
$a > $b => 'a is greater than b',
$a < $b => 'a is less than b',
default => 'a and b are not comparable',
};