解析JSON：意外字符

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);
    });
}