use util\Date;
use lang\IllegalArgumentException;

public function serialize($arg) {
  return switch ($arg) {
    case true      => 'b:1;';
    case false     => 'b:0;';
    case null      => 'N;';
    case is int    => 'i:'.$arg.';';
    case is string => 's:'.strlen($arg).'"'.$arg.'";';
    case is Date   => '@:'.$arg->getTime().';';
    default        => throw new IllegalArgumentException('Unhandled '.typeof($arg));
  };
}