What does the Interface object means in the function parameters : <p>I am not able to understand what is the meaning of having any model or interface object into the method parameters. 
For example, </p>

<pre><code>public function checkRights(CommentInterface $comment)
{
    return true;
}
</code></pre>

<p>so here what does CommentInterface do? why we are not only passing $comment here? How do you name this kind of thing in programming language?</p>

<p>I am new to object oriented php
Thanks.</p>
