title: What does the keyword "callable" do in PHP
body: <p>To be more exact, the "callable" used in function declaration arguments. like the one below.</p>
  
  <pre><code>function post($pattern, callable $handler) {
      $this-&gt;routes['post'][$pattern] = $handler;
      return $this;
  }
  </code></pre>
  
  <p>How does it benefit us? </p>
  
  <p>why and how do we use it?</p>
  
  <p>Maybe this is very basic for you, however, I've tried searching for it and I was getting no answers. at least, nothing I could understand.</p>
  
  <p>Hoping for a for-dummies answer. I'm new to coding... XD</p>
  
  <p><strong>Edit:</strong> Here's a link to where I copied the above piece of code from: <a href="https://stackoverflow.com/questions/11700603/what-is-the-difference-between-url-router-and-dispatcher">link</a></p>