maybe like this:

```php
const HTTP_METHOD_PURGE_SAME_LOCATION        = 'PURGE';
const HTTP_METHOD_PURGE_SEPARATE_LOCATION        = 'GET';

...

$this->purgeLocation
    ? $this->queueRequest(self::HTTP_METHOD_PURGE_SEPARATE_LOCATION, $this->purge_location.$url);
    : $this->queueRequest(self::HTTP_METHOD_PURGE_SAME_LOCATION, $url)
;
```