I am having a problem displaying data from a php page and outputting on a page in a div tag. can anyone help me. this is what i have done so far

HTML
Code:
include ('scripts/connect_to_db.php');
	             //Search the Database to check to see if the product in the database column matches the select product and order it by descending order
				$lftresult = mysqli_query($conn,"SELECT distinct genre FROM video WHERE mediatype='".$cat."' GROUP BY genre");	
					while($leftrow = mysqli_fetch_array($lftresult))
					{ 
						$genre = $leftrow["genre"];
						?>
						
						<div class='left-choicediv'><!--specialoffer-divs-cols-->
							<input type="button" class="cat" id="catlink" value="<?php echo $genre; ?>" onclick="sendcat(this.value);" />
							<input type="hidden" name="cattype" id="cattype" value="<?php echo $cat; ?>" />
						</div><!-- End of left-choicediv-->
					<?php
					}
				?>
			</div><!-- End of Left Column-->
			<div class="right-column"><!-- Start of Right Column-->
		
			<div id="rightcol"></div>
			</div><!-- End of Right Column-->
JAVASCRIPT
Code:
function sendcat(elms)
{
	if (window.XMLHttpRequest) 
	{
		//Firefox, Opera, IE7, and other browsers will use the native object
		var k = new XMLHttpRequest();
	} 
	else 
	{
		//IE 5 and 6 will use the ActiveX control
		var k = new ActiveXObject("Microsoft.XMLHTTP");
	}
	
	var cattype = document.getElementById(cattype).value;
	k.onreadystatechange = function() 
	{
		if (k.readyState == 4 && k.status == 200) 
		{
			document.getElementById("rightcol").innerHTML = k.responseText;
		}
	}
	
	k.open("GET","sendcat.php?catchoice="+elms+"&cattype="+cattype,true);
    // Send the data to PHP now... and wait for response to update the status div
    k.send(null); // Actually execute the request
   // document.getElementsByClassName("right-column").innerHTML = "images/loading/ajax-loader.gif";
}
PHP
Code:
<?php 
		include ('scripts/connect_to_db.php');
		$cat = $_GET['catchoice'];
		$cattype = $_GET['cattype'];
		
		//If A user puts less than 5 exit
		if (($cat == "all") || ($cat == "")) 
		{
			$catchoices = mysqli_query($conn,"SELECT videoID,title,upload_path,thumb FROM video ORDER BY title") 
			or die(mysqli_error($conn)); 
		}
		//If A user puts more than 5 exit
		else 
		{
			$catchoices = mysqli_query($conn,"SELECT videoID,title,upload_path,thumb FROM video WHERE mediatype='".$cattype."' AND genre='".$cat."' ORDER BY title") 
			or die(mysqli_error($conn)); 
		}	
		
			echo $catchoices;
			
			$num_rows = mysqli_num_rows($catchoices);
			
			echo "<h2>".$cat."</h2>";	
			
			if ($num_rows == 0) 
			{
				echo "<p id='notfound'>There are no  available</p>";
			}
			else 
			{
				while($pdrows = mysqli_fetch_array($catchoices))
				{ 
					$vidid = $pdrows["videoID"];
					$prdtitle = $pdrows["title"];
					$upload_path = $pdrows["upload_path"]; 
					$thumb = $pdrows["thumb"];

					echo "<div class='product-divs'><!--product-divs-->";
					echo  "<h3>".$prdtitle."</h3>";
					echo  "<a href='product_details.php?vid=".$vidid."'><img src=".$upload_path.$thumb." alt='".$thumb."' border='0' /></a>";
					echo  "</div><!-- End of product-divs-->";
				}
			}	
?>
I Don't know where I'm Making a Mistake