Hmm, That strage. It works OK on my site:
It seems for some reason your $sData array has not been assigned a value yet. Maybe try replacing $sData with $_GET like this:
PHP Code:
<h1 id="advSearchDefaultHeading">Search Results For: <?php echo $_GET['keyword']; ?></h1>
$_GET['keyword'] should work as long as the keyword is present in the url of the page.