title: Determine whether Array 1 contains all values from Array 2
body: <p>I have 2 arrays which might look something like this:</p>
  
  <pre><code>$a1 = array('c','b','a');
  $a2 = array('a', 'b', 'c', 'd', 'e');
  </code></pre>
  
  <p>I need to somehow check whether every value in <code>$a1</code> is present in <code>$a2</code>.</p>
  
  <p>I've looked at <code>array_diff</code> and <code>array_intersect</code> but can't see how they can be used because the only return the values that are present and not present respectively.</p>