title: PHP case-insensitive in_array function
body: <p>Is it possible to do case-insensitive comparison when using the <code>in_array</code> function?</p>
  
  <p>So with a source array like this:</p>
  
  <pre><code>$a= array(
   'one',
   'two',
   'three',
   'four'
  );
  </code></pre>
  
  <p>The following lookups would all return true:</p>
  
  <pre><code>in_array('one', $a);
  in_array('two', $a);
  in_array('ONE', $a);
  in_array('fOUr', $a);
  </code></pre>
  
  <p>What function or set of functions would do the same? I don't think <code>in_array</code> itself can do this.</p>