PHP类常量为Enums

Question

Using class constants in PHP, is it possible to enforce that an argument must be one of the constants (like an Enum)?

Class Server {
    const SMALL = "s";
    const MEDIUM = "m";
    const LARGE = "l";

    private $size;

    public function __construct($size) {
        $this->size = $size
    }
}

$small = new Server(Server::SMALL); // valid
$foobar = new Server("foobar");      // also valid. This should fail instead

The case of new Server("foobar") should fail, but because the constructor does not validate $size this works. For brevity I only listed three constant sizes, but assume there are N number of sizes so don't want to do a big block of if checks.

Answer 1

Consider using the myclabs/php-enum package, which provides the functionality you are looking for.

If you try to pass an invalid enum value, an exception will be thrown.

Package docs: https://github.com/myclabs/php-enum#documentation