How to hide parts of a page

In my script, I'm using a php echo statement to 'print' info that was entered in a form on a new page.

Can someone tell me how I can make sure a certain part of the info on the new page is not visible when the according form field is left blank?

Example:

Form:

<form id="form1" name="form1" method="post" action="result.php">
My name is<br />
  <label>
  <input type="text" name="textfield" />
  </label>
<p>Site:</p>

  <label>
  <input type="text" name="textfield2" />
  </label>

<p>Extra info:</p>

  <label>
  <textarea name="textarea"></textarea>
  </label>

<p>&nbsp; </p>

  <label>
  <input type="submit" name="Submit" value="Submit" />
  </label>
</form>

PHP:

Output:

<p>Hi<em> <?PHP echo $_POST["textfield"];?> 
</em></p>
<p>You've registered <em> <?PHP echo $_POST["textfield2"];?>  </em>as your site.</p>
<p>This is your extra info: <em>  <?PHP echo $_POST["textarea"];?> </em></p>
<p>&nbsp; </p>

PHP:

If the text area next to 'Extra info' is left blank, I want to hide this part on the output screen:

<p>This is your extra info: <em>  <?PHP echo $_POST["textarea"];?> </em></p>
<p>&nbsp; </p>

PHP:

 

You can use conditional statements. Check to make sure that each textarea is not blank, and if not, then output everything. Like so:

$someText = $_POST['textfield'];
if($someText != "") { // not empty
echo "<p>This is your extra info: <em>$someText</em></p><p>&nbsp;</p>";
}

PHP:

That way it would only print all of that if there was some value inside of $_POST['textfield']