AJAX and PHP

Client-Side Techniques with Smarter JavaScript
}
}
}
// (use xmlHttp.responseXML to read an XML response as a DOM object)
// do something with the response
// ...
// ...
Once again we can successfully use try/catch to handle errors that could happen while initiating a
connection to the server, or while reading the response from the server.
A safer version of the handleRequestStateChange method looks like this:
// function executed when the state of the request changes
function handleRequestStateChange()
{
// continue if the process is completed
if (xmlHttp.readyState == 4)
{
// continue only if HTTP status is "OK"
if (xmlHttp.status == 200)
{
try
{
// retrieve the response
response = xmlHttp.responseText;
// do something with the response
// ...
// ...
}
catch(e)
{
// display error message
alert("Error reading the response: " + e.toString());
}
}
else
{
// display status message
alert("There was a problem retrieving the data:\n" +
xmlHttp.statusText);
}
}
}
OK, let's see how these functions work in action.
Time for Action—Making Asynchronous Calls with XMLHttpRequest
1. In the foundations folder, create a subfolder named async.
2. In the async folder, create a file called async.txt, and add the following text to it:
Hello client!
3. In the same folder create a file called async.html, and add the following code to it:
AJAX Foundations: Using XMLHttpRequest
Hello, server!
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