Detailed explanation of PHP8 new feature match expression

PHP8 alpha2 has been released, and recently introduced a new keyword: match. The function of this keyword is somewhat similar to switch.

I think this is somewhat interesting, and the word match is also very nice, so what does it do?

In the past, we may often use switch to do value conversion work, similar to:

function convert($input) {
    switch ($input) {
        case "true":
            $result = 1;
        break;
        case "false":
            $result = 0;
        break;
        case "null":
            $result = NULL;
        break;
    }
    return $result;
}

Then if we use the match keyword, it can become similar to:

function converti($input) {
    return match($input) {
        "true" => 1,
        "false" => 0,
        "null" => NULL,
    };
}

Compared with switch, match will return the value directly, and the $result intermediate variable in the switch example above is no longer needed.

And, similar to the multiple cases of switch and one block, multiple conditions of match can also be written together, such as:

return match($input) {
    "true", "on" => 1,
    "false", "off" => 0,
    "null", "empty", "NaN" => NULL,
};

It should be noted that it is different from switch. In the past We may often encounter this weird problem when using switch:

$input = "2 person";
switch ($input) {
    case 2:
        echo "bad";
    break;
}

You will find that bad is actually output. This is because switch uses loose comparison (==). Match will not have this problem. It uses strict comparison (===), which means that the value and type must be completely equal.

Also, when the input cannot be satisfied by all the conditions in the match, match will throw an UnhandledMatchError exception:

function convert($input) {
    return match($input) {
        "true" => 1,
    };
}
convert("false");

will get:

Fatal error: Uncaught UnhandledMatchError: Unhandled match value of type string

like this There is no need to worry about unpredictable errors caused by incomplete match conditions.

Recommended tutorial: "PHP8"

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