jQuery.AJAX post() - a few questions and issues - php

Question

I'm making a site where a user spams a button and increases their score in doing so.
I don't want the page to refresh when the button is clicked, so I wanna use AJAX to send the data to the server. Here's what I have so far:
<script type="text/javascript" src="http://code.jquery.com/jquery-1.4.3.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$("#update").click(function() {
$.ajax({
type: "POST",
url: "update.php",
data: "increase",
dataType: "Boolean",
success: function(update) {}
});
});
});
</script>
<button id="update" type="button">Button</button>
<div id="counter"></div>
It's not much at all, I know, but I'm very new to this stuff. The main problem I'm having is with the syntax that you're supposed to use. I want the server to return a Boolean variable if the request is successful, so would I have Boolean in the 'Data Type' in inverted commas, apostrophes or what?
Also, I'm struggling with grasping how the ajax script knows whether it's successful. Is there gonna be something in the 'update.php' script that will return a 'TRUE' or 'FALSE' value?
Finally, the data that's gonna be sent to the php file is supposed to tell the php to update the mysql table with the new score. How should I go about telling the php to update the mysql if it receives the data that the ajax is sending?
Thanks a lot

Answer 1

Something along the lines of this should work:
$.ajax({
type: "POST",
url: "update.php",
data: {"action":"increase"},
success: function(response) {
if(response.error) {
alert(response.error);
return;
}
if(response === 'true') {
//do something
} else {
//do something else
}
}
)};
On the PHP end, your code would likely look like this:
<?php
if(!isset($_POST['action'])) {
echo '{"error": "You must provide a action"}';
exit;
}
$action = $_POST['action'];
if(!in_array($action, array('increase', 'decrease')) die('{"error":"invalid parameters"}');
$action = ($action == 'increase') ? ' + 1' : ' - 1';
//$db is assumed to be a live mysqli object from here on out...
$result = $db->query("UPDATE someTable SET fieldname = fieldname {$action} LIMIT 1;");
echo ($result->affected_rows > 0) ? 'true' : 'false';
?>

Answer 2

The dataType attribute is one of json, xml, html, jsonp, text, or script. Boolean isn't one of the expected types. In this case, you don't want to pay attention to those expected types. jQuery makes an intelligent guess about the type if you pass nothing in based on the MIME type returned by your server.
What you want to do is create a function that will be called by the success callback.
$.ajax({
type: "POST",
url: "http://www.server/path/to/update.php",
data: "increase",
success: function(data, status, xhr) {
functionToProcess(new Boolean(data));
}
)};
The function that is given as an argument to success (an anonymous function, in this case) is called when the Ajax call is complete with a 200 value. Because Ajax is asynchronous (that's what the A is), returning things will do you no good. What you want to do is call another function that will process your boolean value. This I've called functionToProcess in my sample code. For more information, check out the jQuery docs on .ajax().
You can learn about what String values in Javascript produce true versus false boolean values here.

Answer 3

This syntax should work
$(document).ready(function(){
$("#update").click(function(){
$.ajax({type: "POST",
url: "update.php",
data: "increase",
success: function(update) {
if(update)
$("#anyelement").html("Thanks");
else
$("#anyelement").html("Try again !");
}
});
});
});
You can ignore the datatype, because you can parse from any direction
how the ajax script knows whether it's successful
If I understand your point, as far as there is a return to the ajax function the process is success, it is upto you to parse the return and implement the logic.
from you php you do like this:
if(you logic is correct){
//update you database and ... other login goes here
return true;
}else{
return false;
}