title: what does this mean return($var & 1);
body: <p>in PHP in the line below <code>return($var &amp; 1);</code> What does this mean, what does the &amp; mean in this context?</p>
  
  <pre><code>&lt;?php
  function test_odd($var)
  {
  return($var &amp; 1);
  }
  
  $a1=array("a","b",2,3,4);
  print_r(array_filter($a1,"test_odd"));
  ?&gt;
  </code></pre>