laravel - How to understand how to write this method in PHP object-oriented?

Question

I accidentally saw this writing method on a blog today. I have never used it before and I am not sure what it means. I am here to ask you for advice:

Directly upload the picture:

May I ask everyone:

public function getAllPosts() : Callection
{
      // some code
}

How to understand the Callection after this colon?

Answer 1

New feature of php7, specify the type of returned data. . .
Same as int main() in c language