BàI 1: TỔng quan về asp

1.XMLHttp GET Requests

$sID = $_GET["id"];

$sInfo = "";

$sDBServer = "your.databaser.server";

$sDBName = "your_db_name";

$sDBUsername = "your_db_username";

$sDBPassword = "your_db_password";

$sQuery = "Select * from Customers where CustomerId=".$sID;
$oLink = mysql_connect($sDBServer,$sDBUsername,$sDBPassword);

@mysql_select_db($sDBName) or $sInfo="Unable to open database";

if($oResult = mysql_query($sQuery) and mysql_num_rows($oResult) > 0) {

$aValues = mysql_fetch_array($oResult,MYSQL_ASSOC);

$sInfo = $aValues['Name']."
".$aValues['Address']."
".

$aValues['City']."

$aValues['Zip']."

Phone: ".$aValues['Phone']."
".

"".

} else {

}

?>

As you can see, there are no visible HTML or JavaScript calls in the page. All the main logic remains the same, but there are two additional lines of PHP code. The first occurs at the beginning, where the header() function is used to set the content type of the page. Even though the page will return an HTML snippet, it's fine to set the content type as text/plain, because it's not a complete HTML page (and therefore wouldn't validate as HTML). You should always set the content type in any page that is sending non-HTML to the browser. The second added line is towards the bottom, where the $sInfo variable is output to the stream by using the echo command.

Enter customer ID number to retrieve information:

Customer ID:

onclick="requestCustomerInfo()" />

The requestCustomerInfo() function previously created a hidden iframe but now must be changed to use XMLHttp:

function requestCustomerInfo() {

var sId = document.getElementById("txtCustomerId").value;

var oXmlHttp = zXmlHttp.createRequest();

oXmlHttp.open("get", "GetCustomerData.php?id=" + sId, true);

oXmlHttp.onreadystatechange = function () {

if (oXmlHttp.readyState == 4) {

if (oXmlHttp.status == 200) {

displayCustomerInfo(oXmlHttp.responseText);

} else {

oXmlHttp.statusText);

}

}

};

}

Note that the function begins the same way, by retrieving the ID the user entered. Then, an XMLHttp object is created using the zXml library. The open() method is called, specifying an asynchronous GET request for GetCustomerData.php (which has the aforementioned ID added to its query string). Next comes the assignment of the event handler, which checks for a readyState of 4 and then checks the status of the request. If the request was successful (status of 200), the displayCustomerInfo() function is called with the response body (accessed via responseText). If there was an error (status is not 200), then the error information is passed to displayCustomerInfo().