PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

874 Chapter 34 Building Web 2.0 Applications with Ajax
The value of params is then sent to the back-end PHP script in the last line of the function:
myReq.send(params);
Before the values are sent, three request headers are also sent so that the server knows
how to handle the data sent in the POST request:
myReq.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
myReq.setRequestHeader("Content-length", params.length);
myReq.setRequestHeader("Connection", "close");
The next step in this process is to create the JavaScript function to handle the server
response; we have called this addBMResponse:
myReq.onreadystatechange = addBMResponse;
Again, this code is similar to the theHTTPResponse function created earlier in the chapter.The
code for addBMResponse is seen in Listing 34.7.
Listing 34.7
The JavaScript Function addBMResponse()
function addBMResponse() {
if (myReq.readyState == 4) {
if(myReq.status == 200) {
result = myReq.responseText;
document.getElementById('displayresult').innerHTML = result;
} else {
alert('There was a problem with the request.');
}
}
}
This JavaScript function first checks the state of the object; if it has completed its
process, it next checks that the response code from the server was 200 (OK). If the
response code is not 200, an alert is shown with the words “There was a problem with
the request.” Any other responses will come from the execution of the add_bms.php
script and will be displayed in a div with an id value of displayresult. For the
moment, the displayresult id is defined in the new_ss.css style sheet as follows (a
white background):
#displayresult {
background: #fff;
}