title: Missing Parameter in PHP $_POST Function
body: <p>I am using CodeIgniter to pass some parameters to my PHP page through <code>$_POST</code> request, and in the PHP page I am reading. </p>
  
  <pre><code>$foo = $this-&gt;input-&gt;post('myParam');
  </code></pre>
  
  <p>If the <code>myParam</code> parameter is present in the <code>$_POST</code> request, then <code>$foo</code> will be assigned the <code>myParam</code> value. How do I check if <code>myParam</code> is <strong>not passed</strong>  in the <code>$_POST</code> request?</p>