PHP - 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:

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

<!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>PHP中文网</title>
     <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 will perform 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 (containing the drop-down list Content

xml file

<CATALOG>
    <CD>
        <TITLE>Empire Burlesque</TITLE>
        <ARTIST>Bob Dylan</ARTIST>
        <COUNTRY>USA</COUNTRY>
        <COMPANY>Columbia</COMPANY>
        <PRICE>10.90</PRICE>
        <YEAR>1985</YEAR>
    </CD>
    <CD>
        <TITLE>Maggie May</TITLE>
        <ARTIST>Rod Stewart</ARTIST>
        <COUNTRY>UK</COUNTRY>
        <COMPANY>Pickwick</COMPANY>
        <PRICE>8.50</PRICE>
        <YEAR>1990</YEAR>
    </CD>
    <CD>
        <TITLE>Black angel</TITLE>
        <ARTIST>Savage Rose</ARTIST>
        <COUNTRY>EU</COUNTRY>
        <COMPANY>Mega</COMPANY>
        <PRICE>10.90</PRICE>
        <YEAR>1995</YEAR>
    </CD>
    <CD>
        <TITLE>The dock of the bay</TITLE>
        <ARTIST>Otis Redding</ARTIST>
        <COUNTRY>USA</COUNTRY>
        <COMPANY>Atlantic</COMPANY>
        <PRICE>7.90</PRICE>
        <YEAR>1987</YEAR>
    </CD>
</CATALOG>

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

1. PHP creates an XML DOM object

2. Finds all <artist> elements that match the data passed by JavaScript Name

3. Output the album information and send back "txtHint" placeholder

Program result display:

Continuing Learning

new file

<CATALOG> <CD> <TITLE>Empire Burlesque</TITLE> <ARTIST>Bob Dylan</ARTIST> <COUNTRY>USA</COUNTRY> <COMPANY>Columbia</COMPANY> <PRICE>10.90</PRICE> <YEAR>1985</YEAR> </CD> <CD> <TITLE>Sylvias Mother</TITLE> <ARTIST>Dr.Hook</ARTIST> <COUNTRY>UK</COUNTRY> <COMPANY>CBS</COMPANY> <PRICE>8.10</PRICE> <YEAR>1973</YEAR> </CD> <CD> <TITLE>Maggie May</TITLE> <ARTIST>Rod Stewart</ARTIST> <COUNTRY>UK</COUNTRY> <COMPANY>Pickwick</COMPANY> <PRICE>8.50</PRICE> <YEAR>1990</YEAR> </CD> <CD> <TITLE>Black angel</TITLE> <ARTIST>Savage Rose</ARTIST> <COUNTRY>EU</COUNTRY> <COMPANY>Mega</COMPANY> <PRICE>10.90</PRICE> <YEAR>1995</YEAR> </CD> <CD> <TITLE>The dock of the bay</TITLE> <ARTIST>Otis Redding</ARTIST> <COUNTRY>USA</COUNTRY> <COMPANY>Atlantic</COMPANY> <PRICE>7.90</PRICE> <YEAR>1987</YEAR> </CD> </CATALOG>

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