AJAX and PHP

Server-Side Techniques with PHP and MySQL
}
// if the response is long enough, or if it is void, we assume we just
// received a server-side error report
if(response.length > 5 || response.length == 0)
throw(response.length == 0 ? "Server error" : response);
// obtain a reference to the element on the page
myDiv = document.getElementById("myDivElement");
// display the HTML output
if (response >= minServerBufferLevel)
{
// display new message to user
myDiv.innerHTML += "Server buffer level is at " + response + "%, "
+ "starting to retrieve new numbers. ";
// increases counter to start retrieving new numbers
requestsCounter++;
// reinitiate sequence
setTimeout("process();", updateInterval * 1000);
}
else
{
// display new message to user
myDiv.innerHTML += "Server buffer is too low (" + response + "%), "
+ "will check again in " + updateIntervalIfServerBusy
+ " seconds. ";
// reinitiate sequence
setTimeout("process();", updateIntervalIfServerBusy * 1000);
}
// function called when the state of the HTTP request changes
function handleGettingNumber()
{
// when readyState is 4, we are ready to read the server response
if (xmlHttp.readyState == 4)
{
// continue only if HTTP status is "OK"
if (xmlHttp.status == 200)
{
try
{
// do something with the response from the server
getNumber();
}
catch(e)
{
// display error message
alert("Error receiving new number:\n" + e.toString());
}
}
else
{
// display status message
alert("Error receiving new number:\n" + xmlHttp.statusText);
}
}
}
// handles the response received from the server
function getNumber()
{
// retrieve the server's response
var response = xmlHttp.responseText;
// if the response is long enough, or if it is void, we assume we just
// received a server-side error report
if(response.length > 5 || response.length == 0)
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