Can't get data back from an Ajax get request - php

Question

Been playing with this for too long now!
I'm using codeigniter.
I am trying to get some data back from an Ajax get request. Simply I want to check a MySQL DB to check if there is some data in there mathcing a given date. A simple true or false will be fine for the return.
Here is my request, followed by the PHP. The PHP does return the correct result into $data, but when it gets back to the Ajax request, the alert(data) is called and shows up as blank... nothing there.
Any ideas what I'm doing wrong?
Thanks
function get_appointment_data(request_date){
$.ajax({
url: 'http://localhost/doctor_today/booking/retrieve_cal_data',
type: 'GET',
data: request_date,
success: function(data){
alert(data);
}
});
}
function retrieve_cal_data() {
$this->load->model('Booking_model');
$date = $this->input->get('date');
$data = $this->Booking_model->get_calendar_data($date);
return $data==null;
}

Answer 1

I am not familiar with codeigniter but you must output the result of the function. Instade of 'return' you must use 'echo' to return result to ajax request.

Answer 2

You have to echo the result, otherwise your ajax won't receive a result and the success handler won't execute. Here is what I'm going to use for this case, I'm using the simpler .post function for that task with one key difference - I specify 'json' at end of it which means I'll get a json object as a result from my .post (you can search Google for this). The next key is to use encode the result I wanna get in json format using PHP's json_encode function and echo its result. We don't really need to return a result via the normal 'return' statement. So...
The script:
var url = 'http://example.com/ajax_function';
var data = null;
$.post(url, data, function(data) {
if(data.ok)
alert('Everything is fine!');
else
alert('Ops!');
}, 'json');
The server side:
function retrieve_cal_data() {
$this->load->model('Booking_model');
$date = $this->input->get('date');
$data = $this->Booking_model->get_calendar_data($date);
echo json_encode(array('OK' => $data==null));
}
If you call directly the PHP function it should output something like
{ "OK": "true" }
which later on will be translated to an javascript array
data[OK] = true;
which you can use as you wish.
Cheers,
Stan.
P.S. I haven't tested the code but it should pretty work.