title: php function array_key_exists and regular expressions
body: <p>Is it possible to use a regular expression with the php function <code>array_key_exists()</code>?</p>
  
  <p>For example:</p>
  
  <pre><code>$exp = "my regex";  
  array_key_exists($exp, $array);
  </code></pre>
  
  <p>Thank you!</p>