Parsing JSON : unexpected character - php

Question

This question is related to a previous one I wrote here.
Is this JSON syntax correct ? I need it to make a jqPlot chart after.
[{"Date":"2012-02-29","Close":"87.60"},{"Date":"2012-02-28","Close":"87.77"},{"Date":"2012-02-27","Close":"88.07"}]
I ask this because I can't use jQuery.parseJSON(jsonString); or JSON.parse(jsonString); with this string. Firefox returns :
SyntaxError: JSON.parse: unexpected character # index2.php:677
Here is the PHP code that generates it :
<?php
$req = $bdd->prepare('SELECT Date, Close FROM quotes WHERE Symbol = ? AND Date > ? AND Date < ?');
$req->execute(array($_GET['id'], $_GET['datemin'], $_GET['datemax']));
$test=array();
while ($donnees = $req->fetch(PDO::FETCH_ASSOC))
{
// echo print_r($donnees) . "<br />";
// echo $donnees[Date] . "<br />";
$test[] = $donnees;
}
echo json_encode($test);
?>
I don't know what's wrong.
EDIT : Javascript code added.
<script>
$("button").click(function(){
$.get("requete_graph.php", {
id: param1,
datemin: param2,
datemax: param3
}, function(data,status){
console.log(data);
make_graph(data);
}, "json");
});
function make_graph(toto) {
alert("String before : " + JSON.stringify(toto));
var json_parsed = JSON.parse(toto);
alert("String after : " + JSON.stringify(json_parsed));
$(document).ready(function(){
var plot1 = $.jqplot('chartdiv', json_parsed);
});
}
</script>

Answer 1

The JSON is indeed valid (you can check it at jsonlint.com
Your problem might be arising due to extra non whitespace characters being sent after the JSON (for example: PHP errors/warnings). A good way to guarantee that nothing else is output after your JSON is using PHP's die function to send content then stop executing.
die(json_encode($test));
// OR
echo json_encode($test);
die();

Answer 2

At the top of your PHP script, add:
header('Content-type: text/json; charset=utf-8');
If you don't have it, the server will send it as plain text, and your browser won't know that it is a json string.

Answer 3

jQuery.get, given the right dataType parameter (which you did) or a content-type header, does already parse the JSON for you. Your callback function receives an array as the data parameter, not a string.
var json_parsed = JSON.parse(toto);
will then throw an error as toto is not a JSON string (your FF seems to .toString() the array, and then encounters and invalid character). Instead, just use
function make_graph(toto) {
console.log(typeof toto, toto);
alert("String before : " + JSON.stringify(toto));
var json_parsed = toto; // or just use `toto` everywhere
$(document).ready(function(){
var plot1 = $.jqplot('chartdiv', json_parsed);
});
}