PHP Example - AJAX and XML

AJAX can be used to communicate interactively with XML files.

AJAX XML Example

The following example will demonstrate how a web page reads information from an XML file through AJAX:

Example

CD info will be listed here...

Example explanation - HTML page

When the user is in When a CD is selected in the drop-down list above, a function named "showCD()" will be executed. This function is triggered by the "onchange" event:

<html>
<head>
<script>
function showCD(str)
{
      if (str=="")
      {
              document.getElementById("txtHint").innerHTML="";
              return;
      } 
      if (window.XMLHttpRequest)
      {
             // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行
             xmlhttp=new XMLHttpRequest();
      }
      else
      {
            // IE6, IE5 浏览器执行
            xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
      xmlhttp.onreadystatechange=function()
      {
            if (xmlhttp.readyState==4 && xmlhttp.status==200)
            {
                 document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
            }
      }
      xmlhttp.open("GET","getcd.php?q="+str,true);
      xmlhttp.send();
}
</script>
</head>
<body>
<form>
Select a CD:
<select name="cds" onchange="showCD(this.value)">
<option value="">Select a CD:</option>
<option value="Bob Dylan">Bob Dylan</option>
<option value="Bonnie Tyler">Bonnie Tyler</option>
<option value="Dolly Parton">Dolly Parton</option>
</select>
</form>
<div id="txtHint"><b>CD info will be listed here...</b></div>
</body>
</html>

showCD() function performs the following steps:

Check Whether a CD is selected
Create an XMLHttpRequest object
Create a function that executes when the server response is ready
Send a request to a file on the server
Please note the parameter (q) added to the end of the URL (contains the contents of the drop-down list)

PHP file

The server page called above through JavaScript is a PHP file named "getcd.php".

The PHP script loads the XML document, "cd_catalog.xml", runs the query against the XML file, and returns the results in HTML:

<?php
$q=$_GET["q"];
$xmlDoc = new DOMDocument();
$xmlDoc->load("cd_catalog.xml");
$x=$xmlDoc->getElementsByTagName('ARTIST');
for ($i=0; $i<=$x->length-1; $i++)
{
      // 处理元素节点
      if ($x->item($i)->nodeType==1)
      {
              if ($x->item($i)->childNodes->item(0)->nodeValue == $q)
              {
                     $y=($x->item($i)->parentNode);
              }
       }
}
$cd=($y->childNodes);
for ($i=0;$i<$cd->length;$i++)
{ 
      // 处理元素节点
      if ($cd->item($i)->nodeType==1)
      {
            echo("<b>" . $cd->item($i)->nodeName . ":</b> ");
            echo($cd->item($i)->childNodes->item(0)->nodeValue);
            echo("<br>");
      }
}
?>

When a CD query is sent from JavaScript to a PHP page, what happens is: