AJAX and PHP

Server-Side Techniques with PHP and MySQL
A popular (and more powerful) alternative to using file_get_contents is a library
called Client URL Library (CURL). You can find more details about CURL from
http://curl.haxx.se, http://www.php.net/curl and http://www.zend.com/
zend/tut/tutorial-thome3.php. For basic needs though, file_get_contents gets the
job done nicely and easily.
Let's try this out with some code. The functionality we want to implement is the same as in
the previous exercise (get a random number and display it), but this time it will work with
all browsers.
Time for Action—Using a Proxy Server Script to Access Remote Servers
1. In the foundations folder, create a subfolder named proxyping.
2. In the proxyping folder, create proxyping.html:
Practical AJAX: Accessing Remote Server through Proxy PHP
Script
Server, tell me a random number!
3. In the same folder create proxyping.js. Note that this file is similar to ping.js, and
the new bits are highlighted. (We removed the bits that handle Mozilla security from
process(), changed the server address in the header, removed the num parameter
because in this scenario we'll only request one number at a time, and added an errorhandling
measure.)
// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();
// holds the remote server address and parameters
var serverAddress = "proxyping.php";
var serverParams = "&min=1" + // the min number to generate
"&max=100"; // the max number to generate
// creates an XMLHttpRequest instance
function createXmlHttpRequestObject()
{
// will store the reference to the XMLHttpRequest object
var xmlHttp;
// this should work for all browsers except IE6 and older
try
{
// try to create XMLHttpRequest object
xmlHttp = new XMLHttpRequest();
}
catch(e)
{
// assume IE6 or older
var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
"MSXML2.XMLHTTP.5.0",
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