I would not recommend this long line for readability purpose.
What about this alternative:

``` php
    protected function magentoCategoryExist(Category $category, array $magentoCategories, $magentoUrl)
    {
        if (!$id = $this->getMagentoCategoryId($category, $magentoUrl)) {
            return;
        }
        
        return isset($magentoCategories[$id]);
    }
```