PHP 関数のパラメータの型を確認するにはどうすればよいですか?

function greet($name) {
    $type = gettype($name);
    echo "Name is of type $type: ";
    echo "Name value: $name";
}

$func = new ReflectionFunction('greet');
foreach ($func->getParameters() as $parameter) {
    echo "Parameter $parameter->name is of type ";
    $type = $parameter->getType();
    echo $type ? $type->getName() : 'unset';
}

function validateEmail($email) {
    $type = gettype($email);
    if ($type !== 'string') {
        throw new InvalidArgumentException("Email must be a string");
    }
    // Validate the email address here...
}