I am following the code with declare(strict_types=1);

In the Validator::email method I was declaring the return value to be bool and using return filter_var..., but when the email is correct, filter_var actually returns a string.

What would be the best approach here, to create a condition to return bool or to omit the return type of the method?

I kept the return type declaration and created a $filtered_value var to receive the return of filter_var, than returned !!$filtered_value in my method. Is this the correct/more used approach?

    public static function email(string $value)
    {
        $filtered_var = filter_var($value, FILTER_VALIDATE_EMAIL);

        return !!$filtered_var;
    }

Extract a Simple Validator Class