title: PHP supports first-class functions, what does it mean
body: <p>What does this statement mean in <code>php</code>, </p>
  
  <blockquote>
    <p>PHP supports first-class functions</p>
  </blockquote>
  
  <p>Would anyone explain briefly, I seems not to understand while reading the documentation.</p>
  
  <p>I would appreciate an example.</p>