JSON parsing an array from PHP filled with SQL data returns [object Object]

Question

I'm trying to make a PHP file retrieve data from a SQL DB with an Ajax call, and store data in JSON format.

Ajax call

$.ajax({
    method:"POST",  
    dataType:"json",
    crossDomain:true,
    url:"getCourses.php", 
    success: function(response){

        var courses=JSON.parse(response);

        var el="";
        for(var i=0;i<courses.length;i++)
        {
            console.log(courses[i].title);
        }

    },
    error: function(request,error){
        console.log("ERROR: Request " + request + "\nSpecific Error: " + error);
    }
});

PHP function

 //this is a test, not the actual SQL query
$query="SELECT * FROM courses ORDER BY id;";
$result=$mysqli->query($query); 
if($result->num_rows >0) //if there is at least one row...
{
    $myArray= array(); //...create an array...
    while($row = $result->fetch_array(MYSQL_ASSOC)){ //...fetch it...

        $myArray[]=$row; //...and add its row to $myArray ([] means autoincrement).
    }


    echo json_encode($myArray);

However, the Chrome console just gives me a parserror. I've been bashing my head since yesterday, and I can't seem to find the problem. I know that JSON has trouble with non-UTF8 strings, but even doing a utf8_encode just gives this error.

UPDATED

I've only removed the JSON.parse method as told, and substituted it with

var courses=response;

In the PHP file instead, I've added the headers and this

foreach ($myArray as $row)
    {
        //UTF8 encoding to avoid parsing problems
        htmlentities($row['title'],ENT_QUOTES | ENT_IGNORE, "UTF-8"); 
        htmlentities($row['description'],ENT_QUOTES | ENT_IGNORE, "UTF-8");

    }

before the JSON encode. The Chrome console always returns me this

ERROR: Request [object Object]
Specific Error: parsererror

jeroen · Accepted Answer · 2015-04-29 15:36:38Z

3

You should not parse the json manually:

var courses=JSON.parse(response);

As you have specified the dataType as json, jQuery will parse it already, so response is already an object.

So you just need:

success: function(courses){
    var el="";
    for(var i=0;i<courses.length;i++)
    {
        console.log(courses[i].title);
    }
 },

Note that you always need to output valid json when you specify the dataType like that, so if you if condition in the php script is not met, you should send your error message as json as well.

answered Apr 29, 2015 at 15:36

jeroen

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6 Comments

Kevin Nagurski Over a year ago

Worth sending the valid mime type too header('Content-type: application/json'); just before your echo json_encode($myArray);

jeroen Over a year ago

@KevinNagurski Possibly, but I have never had to use it on the servers I work with.

Kevin Nagurski Over a year ago

not required, but helps the browser and means you can do a manual GET request and have the browser parse the result as JSON rather than display as flat text (very browser dependant) Good answer thought (upvoted :-)

riciloma Over a year ago

It won't work. It returns the same parseerror. I'm using xampp for an Apache test server, maybe I have to edit something in the settings...?

riciloma Over a year ago

Okay, I've managed to resolve the error, it was a utf8_encoding problem. Still, this post remains the best solution, because I need to manipulate the object, and you also explained what does datatype do. Thanks a lot!

|

Alexis Paques · Accepted Answer · 2015-04-29 17:12:42Z

1

You should send the correct headers and save your php file into "UTF-8 without BOM" format.

 header('Cache-Control: no-cache, must-revalidate');
 header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');
 header('Content-type: application/json');

If you still have troubles, you can use this library : Simple JSON for PHP that helps to forge easily a JSON in

answered Apr 29, 2015 at 17:12

Alexis Paques

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2 Comments

Alexis Paques Over a year ago

Add console.log(request) under console.log("ERROR: Request " + request + "\nSpecific Error: " + error);

Alexis Paques Over a year ago

With this you will be able to see the complete error in the console

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