The behavior you're experiencing is expected. PHP interprets query string parameters as strings parse_str('isFeatured=false', $q) and thus "true" and "false" are not automatically recognized as boolean values.

When you use MapQueryString it attempts to map this string value (using the Serializer/PropertyAccess components) to the property specified in your DTO (of type bool in this case) and since PHP treats any non-empty string as true (except for the string "0" which is a special case and is considered false) in a boolean context "true" and "false" will both result in true when cast to boolean.

To handle this, you can implement custom logic in your DTO to manually convert the string "false" to their respective boolean value:

class MyDTO 
{
    // ...

    public function setIsFeatured(string|bool $value): void
    {
        $this->isFeatured = is_string($value) ? 'false' !== $value && '0' !== $value : $value;
    }
}

If you need a more generic or global solution for the entire application, consider a custom ObjectNormalizer. However, be aware that this approach may introduce more complexity in implementing such an assumption, because inferring the property type is not part of the current logic and might decrease the denormalizing performance as well.

public class???