title: How to pass standard php functions to array_map and array_filter?
body: <p>PHP functions such as <code>array_map</code> and <code>array_filter</code> take an array, and a function as arguments.</p>
  
  <p>EG:</p>
  
  <pre><code>$result = array_map(function (el) {
  // do stuff
  }, $elements)
  </code></pre>
  
  <p>Is it possible to pass a standard php function the same way?</p>
  
  <p>Something along the lines of <code>$result = array_map(boolval, $elements)</code></p>
  
  <p><strong>EDIT</strong>
  The above example throws the error <code>Undefined constant boolval</code></p>