Klassen und Objekte

<?php
declare(strict_types=1);

class Konto
{
    private float $stand = 0.0;
    public static int $anzahl = 0;
    public const ZINS = 0.02;

    public function __construct(
        public readonly string $inhaber,        // Constructor Promotion (8.0)
        float $start = 0.0,
    ) {
        $this->stand = $start;
        self::$anzahl++;
    }

    public function einzahlen(float $betrag): static
    {
        if ($betrag <= 0) {
            throw new InvalidArgumentException("Betrag muss positiv sein");
        }
        $this->stand += $betrag;
        return $this;                          // für Verkettung
    }

    public function stand(): float { return $this->stand; }

    public function __toString(): string
    {
        return sprintf("%s: %.2f", $this->inhaber, $this->stand);
    }
}

$k = new Konto("Mia", 100);
$k->einzahlen(50)->einzahlen(25.5);
echo $k, "\n";
echo Konto::$anzahl, " ", Konto::ZINS, " ", $k->inhaber, "\n";
try {
    $k->inhaber = "Tom";                        // readonly
} catch (Error $e) {
    echo $e->getMessage(), "\n";
}
try {
    $k->einzahlen(-5);
} catch (InvalidArgumentException $e) {
    echo "Fehler: ", $e->getMessage(), "\n";
}

<?php
class Punkt { public function __construct(public int $x = 0, public int $y = 0) {} }
$a = new Punkt(1, 2);
$b = $a;               // gleiches Objekt
$c = clone $a;         // Kopie
$b->x = 99;
echo $a->x, " ", $c->x, " ", var_export($a == $c, true), " ", var_export($a === $b, true), "\n";

<?php
class MathHelfer
{
    public const PI = 3.14159;
    public static function kreisflaeche(float $r): float { return self::PI * $r ** 2; }
}
echo MathHelfer::kreisflaeche(2), "\n";

class Nutzer
{
    private function __construct(public string $name) {}
    public static function erstelle(string $name): self { return new self(ucfirst($name)); }   // Fabrikmethode
}
echo Nutzer::erstelle("mia")->name, "\n";

<?php
class Meine
{
    private array $daten = [];
    public function __get($n) { return $this->daten[$n] ?? "?"; }
    public function __set($n, $v) { $this->daten[$n] = $v; }
    public function __call($n, $args) { return "$n(" . implode(",", $args) . ")"; }
    public function __invoke($x) { return $x * 2; }
}
$m = new Meine();
$m->farbe = "rot";
echo $m->farbe, " ", $m->gibtEsNicht, " ", $m->irgendwas(1, 2), " ", $m(21), "\n";

<?php
enum Status: string
{
    case Offen = 'offen';
    case Erledigt = 'erledigt';

    public function label(): string
    {
        return match ($this) {
            self::Offen => "Noch zu tun",
            self::Erledigt => "Fertig",
        };
    }
}
echo Status::Offen->value, " ", Status::from('erledigt')->label(), " ", Status::tryFrom('x')?->label() ?? "unbekannt", "\n";
foreach (Status::cases() as $s) echo $s->name, " ";
echo "\n";