Vererbung, Interfaces und Traits

<?php
abstract class Tier
{
    public function __construct(protected string $name) {}
    abstract public function laut(): string;
    public function vorstellen(): string { return "{$this->name} sagt {$this->laut()}"; }
}

class Hund extends Tier
{
    public function laut(): string { return "Wuff"; }
}

class Katze extends Tier
{
    public function __construct(string $name, private int $leben = 9)
    {
        parent::__construct($name);
    }
    public function laut(): string { return "Miau"; }
    public function vorstellen(): string
    {
        return parent::vorstellen() . " ({$this->leben} Leben)";
    }
}

foreach ([new Hund("Rex"), new Katze("Mimi")] as $t) echo $t->vorstellen(), "\n";
var_dump(new Hund("x") instanceof Tier, get_parent_class(new Hund("x")));

Rex sagt Wuff
Mimi sagt Miau (9 Leben)
bool(true)
string(4) "Tier"

<?php
interface Formatierbar
{
    public function format(): string;
}
interface Vergleichbar
{
    public function vergleiche(self $anderer): int;
}

class Preis implements Formatierbar, Vergleichbar
{
    public function __construct(private float $betrag) {}
    public function format(): string { return number_format($this->betrag, 2, ",", ".") . " €"; }
    public function vergleiche(Vergleichbar $anderer): int { return $this->betrag <=> $anderer->betrag; }
}

function drucke(Formatierbar ...$dinge): void { foreach ($dinge as $d) echo $d->format(), "\n"; }
drucke(new Preis(1234.5), new Preis(9.99));
var_dump((new Preis(5))->vergleiche(new Preis(7)));

1.234,50 €
9,99 €
int(-1)

<?php
class Liste implements Countable, IteratorAggregate, ArrayAccess, JsonSerializable
{
    private array $d = [];
    public function count(): int { return count($this->d); }
    public function getIterator(): Iterator { return new ArrayIterator($this->d); }
    public function offsetExists(mixed $o): bool { return isset($this->d[$o]); }
    public function offsetGet(mixed $o): mixed { return $this->d[$o] ?? null; }
    public function offsetSet(mixed $o, mixed $v): void { if ($o === null) $this->d[] = $v; else $this->d[$o] = $v; }
    public function offsetUnset(mixed $o): void { unset($this->d[$o]); }
    public function jsonSerialize(): mixed { return ["items" => $this->d]; }
}
$l = new Liste();
$l[] = "a"; $l[] = "b"; $l["x"] = "c";
echo count($l), " ", $l[0], " ", isset($l["x"]) ? "ja" : "nein", " ", json_encode($l), "\n";
foreach ($l as $k => $v) echo "$k=$v ";
echo "\n";

3 a ja {"items":{"0":"a","1":"b","x":"c"}}
0=a 1=b x=c

<?php
trait Zeitstempel
{
    private ?string $erstellt = null;
    public function markiere(string $zeit): static { $this->erstellt = $zeit; return $this; }
    public function erstelltAm(): ?string { return $this->erstellt; }
}
trait Logger
{
    public function log(string $m): void { echo "[", static::class, "] $m\n"; }
}

class Artikel { use Zeitstempel, Logger; }
class Kommentar { use Zeitstempel; }

$a = (new Artikel())->markiere("2025-01-01");
$a->log("angelegt " . $a->erstelltAm());
echo (new Kommentar())->erstelltAm() ?? "kein Datum", "\n";

[Artikel] angelegt 2025-01-01
kein Datum

<?php
namespace App\Modell;

class Nutzer {}

echo Nutzer::class, " ", \strlen("abc"), "\n";

App\Modell\Nutzer 3