$tags = array();
$keywords = array();
$keywords[] = "Hello World";
$keywords[] = "Hello world Again";
$keywords[] = "Hello Again";
$keywords[] = "Hello Again one more time";
$keywords[] = "Goodbye Seeya";
$keywords[] = "Pencil";
$keywords[] = "Howto sharpen pencil";
$keywords[] = "Drawing paper";
$keywords[] = "Drawing rocks";

foreach($keywords as $keyword)
	{
	$words = explode(" ",$keyword);
	foreach($words as $word)
		{
		$word = strtolower($word);
		if (isset($tags[$word]))
			{
			$tags[$word] += 1;
			}
		else
			{
			$tags[$word] = 1;
			}
		}
	}
ksort($tags);
foreach($tags as $tag=>$size)
	{
	$size += 7;
	echo "<span style=\"font-size: {$size}px\">$tag</span> ";
	}