title: Check if the GET value is null
body: <p>I have a form that is to be initialized with $_GET of the values posted</p>
  
  <pre><code>&lt;?=form('sentopage')?&gt;
  &lt;input type='text' name='name' value='&lt;?=$_GET['val']?'/&gt;
  &lt;?=form_close()?&gt;
  </code></pre>
  
  <p>This will cause an error if the page is opened with an URL whose 'val' is not there ? I would like to check it first but I don't know how ?</p>
  
  <p>UPDATE</p>
  
  <p>My problem is
  I am with an index page, after I fill in a form in the index page then submit, I will be directed to a confirm page, if I then press the button to confirm I will proceed further, if I press the button to re-edit the submitted information, I will be directed back to the index page but some information I entered previously in the text/textarea should not be deleted; that is why I use "index?info=something&amp;inf=somethingelse" etc. But If I leave this in the main page, the first run of the index page will cause an error in the form. </p>