PHP Magic Methods

<?php
class Connection {
    public function __construct(public string $dsn) {
        echo "Connecting to $dsn\n";
    }

    public function __destruct() {
        echo "Disconnecting {$this->dsn}\n";
    }
}

$c = new Connection("mysql:host=localhost");
// __destruct fires when last reference is dropped (end of scope, unset, etc)

<?php
class Config {
    private array $data = [];

    public function __get(string $name): mixed {
        return $this->data[$name] ?? null;
    }

    public function __set(string $name, mixed $value): void {
        $this->data[$name] = $value;
    }
}

$config = new Config();
$config->host = "localhost";
$config->port = 3306;

echo $config->host;        // "localhost"
echo $config->missing;     // null (no notice)

<?php
class Config {
    private array $data = [];

    public function __isset(string $name): bool {
        return isset($this->data[$name]);
    }

    public function __unset(string $name): void {
        unset($this->data[$name]);
    }
}
// Now isset($config->host) and unset($config->host) work

<?php
class Query {
    private array $wheres = [];

    public function __call(string $name, array $args): self {
        // whereName("Alice") -> name = Alice
        if (str_starts_with($name, "where")) {
            $field = lcfirst(substr($name, 5));
            $this->wheres[$field] = $args[0];
        }
        return $this;
    }

    public function __callStatic(string $name, array $args): self {
        return (new self())->$name(...$args);
    }
}

$q = Query::whereName("Alice")->whereAge(30);

<?php
class Money implements Stringable {
    public function __construct(
        public readonly int $cents,
        public readonly string $currency,
    ) {}

    public function __toString(): string {
        return number_format($this->cents / 100, 2) . " " . $this->currency;
    }
}

$m = new Money(1999, "USD");
echo $m;                       // "19.99 USD"
echo "Price: $m";              // works in interpolation
$str = (string) $m;            // explicit cast

<?php
class Multiplier {
    public function __construct(private int $factor) {}

    public function __invoke(int $n): int {
        return $n * $this->factor;
    }
}

$double = new Multiplier(2);
$triple = new Multiplier(3);

echo $double(5);      // 10
echo $triple(5);      // 15

// Works with array_map etc.
$out = array_map($double, [1, 2, 3]);   // [2, 4, 6]

<?php
class Order {
    public Address $shipTo;

    public function __clone(): void {
        // Deep-clone nested object so copies don't share state
        $this->shipTo = clone $this->shipTo;
    }
}

<?php
class User {
    public function __construct(
        public string $name,
        private string $password,    // dont serialize secrets
    ) {}

    public function __serialize(): array {
        return ["name" => $this->name];  // omit password
    }

    public function __unserialize(array $data): void {
        $this->name = $data["name"];
        $this->password = "";
    }
}

$s = serialize(new User("Ruban", "secret"));
// no "secret" in $s

<?php
class HttpClient {
    private string $apiKey;
    public string $host;
    private array $hugeCache = [];

    public function __debugInfo(): array {
        return ["host" => $this->host, "cacheSize" => count($this->hugeCache)];
    }
}

var_dump(new HttpClient());
// object(HttpClient)#1 (2) { ["host"]=> string(...), ["cacheSize"]=> int(0) }