PHP - AJAX and XML

AJAX can be used for interactive communication with an XML file.
AJAX XML Example
The following example will demonstrate how a web page can fetch information from an XML file with AJAX:
Example: The HTML Page looks like as below

CD info will be listed here...

Example Explained - The HTML Page
When a user selects a CD in the dropdown list above, a function called "showCD()" is executed. The function is triggered by the "onchange" event:
<html> <head>
<script type="text/javascript">
function showCD(str)
{ if (str=="")   {
  document.getElementById("txtHint").innerHTML="";
  return;  }
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();   }
else
  {// code for IE6, IE5
  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="Brittany Spears">Bob Dylan</option>
<option value="Ricky Martin">Bonnie Tyler</option>
<option value="Micheal Jackson">Dolly Parton</option>
</select> </form>
<div id="txtHint"><b>CD info will be listed here...</b></div>
</body> </html>

The showCD() function does the following:
  • Check if a CD is selected
  • Create an XMLHttpRequest object
  • Create the function to be executed when the server response is ready
  • Send the request off to a file on the server
  • Notice that a parameter (q) is added to the URL (with the content of the dropdown list)

The PHP File
The page on the server called by the JavaScript above is a PHP file called "getcd.php".
The PHP script loads an XML document, "cd_catalog.xml", runs a query against the XML file, and returns the result as HTML:
<?php
$q=$_GET["q"];
$xmlDoc = new DOMDocument();
$xmlDoc->load("cd_catalog.xml");
$x=$xmlDoc->getElementsByTagName('ARTIST');
for ($i=0; $i<=$x->length-1; $i++)
{
//Process only element nodes
if ($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++)
{
//Process only element nodes
if ($cd->item($i)->nodeType==1)
  {
  echo("<b>" . $cd->item($i)->nodeName . ":</b> ");
  echo($cd->item($i)->childNodes->item(0)->nodeValue);
  echo("<br />");
  } } ?>
When the CD query is sent from the JavaScript to the PHP page, the following happens:
  1. PHP creates an XML DOM object
  2. Find all <artist> elements that matches the name sent from the JavaScript
  3. Output the album information (send to the "txtHint" placeholder)
PHP - AJAX Live Search
AJAX can be used to create more user-friendly and interactive searches.
AJAX Live Search
The following example will demonstrate a live search, where you get search results while you type.
Live search has many benefits compared to traditional searching:
  • Results are shown as you type
  • Results narrow as you continue typing
  • If results become too narrow, remove characters to see a broader result
The HTML Page looks like as below

Search for a NextStep4IT page in the input field below:



The results in the example above are found in an XML file (links.xml).
Example Explained - The HTML Page
When a user types a character in the input field above, the function "showResult()" is executed. The function is triggered by the "onkeyup" event:
<html> <head>
<script type="text/javascript">
function showResult(str)
{ if (str.length==0)   {
  document.getElementById("livesearch")
.innerHTML="";
  document.getElementById("livesearch")
.style.border="0px";
  return;   }
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();   }
else   {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  } xmlhttp.onreadystatechange=function()
  {   if (xmlhttp.readyState==4 && xmlhttp.status==200)    {
document.getElementById("livesearch").inner
HTML=xmlhttp.responseText;
    document.getElementById("livesearch")
.style.border="1px solid #A5ACB2";
    }   }
xmlhttp.open
("GET","livesearch.php?q="+str,true);
xmlhttp.send(); } </script>
</head> <body> <form>
<input type="text" size="30" onkeyup="showResult(this.value)" />
<div id="livesearch"></div>
</form> </body> </html>
Source code explanation:
If the input field is empty (str.length==0), the function clears the content of the livesearch placeholder and exits the function.
If the input field is not empty, the showResult() function executes the following:

  • Create an XMLHttpRequest object
  • Create the function to be executed when the server response is ready
  • Send the request off to a file on the server
  • Notice that a parameter (q) is added to the URL (with the content of the input field)
  • Php ClassRoom
    The PHP File
    The page on the server called by the JavaScript above is a PHP file called "livesearch.php".

    The source code in "livesearch.php" searches an XML file for titles matching the search string and returns the result:
    <?php
    $xmlDoc=new DOMDocument();
    $xmlDoc->load("links.xml");
    $x=$xmlDoc->getElementsByTagName('link');
    //get the q parameter from URL
    $q=$_GET["q"];
    //lookup all links from the xml file if length of q>0
    if (strlen($q)>0)
    {
    $hint="";
    for($i=0; $i<($x->length); $i++)
      {
      $y=$x->item($i)->getElementsByTagName('title');
      $z=$x->item($i)->getElementsByTagName('url');
      if ($y->item(0)->nodeType==1)
        {
        //find a link matching the search text
        if (stristr($y->item(0)->childNodes->item(0)->nodeValue,$q))
          {       if ($hint=="")         {
            $hint="<a href='" .
            $z->item(0)->childNodes->item(0)->nodeValue .
            "' target='_blank'>" .
            $y->item(0)->childNodes->item(0)->nodeValue . "</a>";
            }       else        {
            $hint=$hint . "<br /><a href='" .
            $z->item(0)->childNodes->item(0)->nodeValue .
            "' target='_blank'>" .
            $y->item(0)->childNodes->item(0)->nodeValue . "</a>";
            }       }     }   } }
    // Set output to "no suggestion" if no hint were found
    // or to the correct values
    if ($hint=="")
      {   $response="no suggestion";   } else  {
      $response=$hint;  }
    //output the response
    echo $response;
    ?> 

    If there is any text sent from the JavaScript (strlen($q) > 0), the following happens:
    • Load an XML file into a new XML DOM object
    • Loop through all <title> elements to find matches from the text sent from the JavaScript
    • Sets the correct url and title in the "$response" variable. If more than one match is found, all matches are added to the variable
    • If no matches are found, the $response variable is set to "no suggestion

     


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