Ajax call not returning data from php file

Question

i am having a little trouble with the following ajax call;

function question()  {
//ajax call to fetch data from database
var course = "St.Andrews";
var dataString = "course=" + course;

$.ajax({
     type:  "GET",
     url:   "http://www.webaddress/fetch.php",
     datatype: "json",
     data: course,

     success: function(datas){
     console.log(datas);
     },
     error: function(XMLHttpRequest, textStatus, errorThrown){
     console.log("error:" + XMLHttpRequest.responsetext);
     }
     });
}

For some reason, i cannot get the fetched results to display. My php file that returns the results works fine if i navigate to it from the browser and i get the returned results in the valid format.

When i check the console log, i can see the params are correct and i get error:undefined. Can anyone provide as to what i'm doing wrong, thanks.

Here is my php script;

<?php
//include databse details
require_once 'login.php';

//connect to database or return error
$db_server = mysql_connect($db_hostname, $db_username, $db_password);
if (!$db_server) die("unable to connect to MYSQL:" . mysql_error());

//select database or return error
mysql_select_db($db_database)
or die("Unable to select database: " . mysql_error());

if (isset($_GET['course'])) {

    $course = $_GET['course'];

    //set the character code
    mysql_query('SET CHARACTER SET utf8');

    //make the query
    $query = "SELECT * FROM questions WHERE course = '" . $course . "' ";
    $result = mysql_query($query) or die (mysql_error());

    if ($result !== false && mysql_num_rows($result) > 0)   {

        $row = mysql_fetch_array($result, MYSQL_ASSOC);

        $question = $row['question'];
        $answer = $row['answer'];
        $incorrect = $row['incorrectAnswer'];
        $difficulty = $row['difficulty'];

        //Json row
        $json = array ("question" => $question, "answer" => $answer, "incorrect" => $incorrect, "difficulty" => $difficulty);
    } else {
        //catch any errors
        $json = array("error" => "Mysql query error");
    }

    //set header for json data
    header("Content-Type: application/json", true);
    //return Json
    echo json_encode($json);
} else {
    echo "Needs course to advance dingbat";
}

Are you making a cross domain request ?

Shyju
– Shyju

2012-03-21 13:36:07 +00:00
Commented Mar 21, 2012 at 13:36 — Shyju
– Shyju, Commented Mar 21, 2012 at 13:36
You should console.log() more in the error CB.

Shikiryu
– Shikiryu

2012-03-21 13:39:56 +00:00
Commented Mar 21, 2012 at 13:39 — Shikiryu
– Shikiryu, Commented Mar 21, 2012 at 13:39

Nicola Peluchetti · Accepted Answer · 2012-03-21 13:37:05Z

1

The most probable reason is that you are calling that url from a different domain and that's not possible using plain json for security reasons, you should use jsonp.

To correct that: js

var course = "St.Andrews";
var dataString = {course: course, callback : "?"};

$.ajax({
     type:  "GET",
     url:   "http://www.webaddress/fetch.php",
     datatype: "jsonp",
     data: course,

     success: function(datas){
     console.log(datas);
     },
     error: function(XMLHttpRequest, textStatus, errorThrown){
     console.log("error:" + XMLHttpRequest.responsetext);
     }
     });
}

php

<?php header('content-type: application/javascript; charset=utf-8');

$data = array(1, 2, 3, 4, 5, 6, 7, 8, 9);

echo $_GET['callback'] . '('.json_encode($data).')';

answered Mar 21, 2012 at 13:37

Nicola Peluchetti

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4 Comments

JPK Over a year ago

thanks for the info, but i could not get this working. I have updated with my php code

Nicola Peluchetti Over a year ago

@JPK but is the call on the same domain or on another?

JPK Over a year ago

i am making the ajax call from a local file on my desktop and will not be placed on the server

JPK Over a year ago

thanks for the information. I used your comments to do a little research and I managed to get it working a treat using http://www.webaddress/jsonp.php?method=getAllUsers&jsoncallback=?

hvgotcodes · Accepted Answer · 2012-03-21 13:36:49Z

1

I see two possibilities:

1) Your php script is not returning valid json. You specify json as the datatype parameter, be sure you are actually returning json.

2) You are violating the same origin policy. Your url is http://www.webadddress/...unless the browser loaded the script from that some url, it won't be able to access that url with an xhr.

answered Mar 21, 2012 at 13:36

hvgotcodes

121k33 gold badges209 silver badges237 bronze badges

1 Comment

JPK Over a year ago

thanks for the feedback, i have updated my code to show my php file

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