Problems sorting list via AJAX/PHP/MySQL

programming web dev
1

I cannot seem to get this sample list (created from a MySQL DB using PHP) to sort via AJAX request. I’m wanting to learn AJAX incorporating PHP but I can’t get this simple alphabet list to work. Nothing happens when I click on my links. Here is the code:

index.php:


<?
include("lib.class.php");
$db_conn->connect_to_db("fadedele_ajaxDB");
?>
<html>
<head>
    <title>Ajax</title>
    <script type="text/javascript" src="global.js"></script>
</head>


<body>

Order By: 
<span id="refreshListOrderAsc" style="color: 335599; cursor: pointer" onClick="orderListBy(ASC);">Ascending</span>
  |  
<span id="refreshListOrderDesc" style="color: ccaa66; cursor: pointer" onClick="orderListBy(DESC);">Descending</span>

<br /><br />
            
<div id="alphabetList">
            
<?

    $alphabet = mysql_query("SELECT * FROM `alphabet` ORDER BY `id` ASC");

    while ($row = mysql_fetch_array($alphabet)) {
        
           $letter = $row['letters'];
        $letterID = $row['id'];
        
?>

<span id="alphabetList"><? echo $letter ?></span><br />

<? } ?>
            
</div>

</body>
</html>

global.js:


// stores the reference to the XMLHttpRequest object
var xmlHttp = createXmlHttpRequestObject(); 

// retrieves the XMLHttpRequest object
function createXmlHttpRequestObject() 
{    
  // will store the reference to the XMLHttpRequest object
  var xmlHttp;
  // if running Internet Explorer
  if(window.ActiveXObject)
  {
    try
    {
      xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch (e) 
    {
      xmlHttp = false;
    }
  }
  // if running Mozilla or other browsers
  else
  {
    try 
    {
      xmlHttp = new XMLHttpRequest();
    }
    catch (e) 
    {
      xmlHttp = false;
    }
  }
  // return the created object or display an error message
  if (!xmlHttp)
 
    alert("Error creating the XMLHttpRequest object.");
  else 
    return xmlHttp;
}

// make asynchronous HTTP request using the XMLHttpRequest object 
function orderListBy(orderByType)
{
  // proceed only if the xmlHttp object isn't busy
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {

    xmlHttp.open("GET", "list.php?orderBy=" + orderByType, true);
    xmlHttp.send(null);
    
    // define the method to handle server responses
    xmlHttp.onreadystatechange = handleServerResponse;
  }
}

// executed automatically when a message is received from the server
function handleServerResponse() 
{
  // move forward only if the transaction has completed
  if (xmlHttp.readyState == 4) 
  {
    // status of 200 indicates the transaction completed successfully
    if (xmlHttp.status == 200) 
    {
      document.getElementById("alphabetList").innerHTML = xmlHttp.responseText;
    } 
    // a HTTP status different than 200 signals an error
    else 
    {
      alert("There was a problem accessing the server: " + xmlHttp.statusText);
    }
  }
}

list.php:


<?

include("lib.class.php");
    
$db_conn->connect_to_db("fadedele_ajaxDB");
    
$orderBy = $_GET['orderBy'];

$alphabet = mysql_query("SELECT * FROM `alphabet` ORDER BY `id` " . $orderBy);

while ($row = mysql_fetch_array($alphabet)) {
        
       $letter = $row['letters'];
    $letterID = $row['id'];
        
?>

<span id="alphabetList"><? echo $letter ?></span><br />

<? } ?>

I know that I am using the GET method correctly because i can go to “/list.php?orderBy=DESC” and it works fine.

Any help would be great! Thanks.