json_encode creating a malformed JSON (with extra hidden character)

I'm using PHP's `json_encode()` to return some data, retrieved by jQuery's `ajax()`: Simplified JS: ``` $.ajax({ dataType: 'json', contentType: 'application/json', cache: false, type: 'POST', url: './api/_imgdown.php', error: function(jqXHR, textStatus, errorThrow) { console.log(jqXHR, textStatus, errorThrow); }, success: function(data, textStatus, jqXHR) { console.log(data, textStatus, jqXHR); } }); ``` The PHP is: ``` header('Content-Type: application/json; charset=UTF-8'); //default apiResponse $apiResponse = [ "status" => 1, "message" => "success", "data" => null ]; ``` Then when php runs my code, it ends by adding this data: ``` $apiResponse['data'][] = [ "mid" => (int)$mid, "card_type" => $card_type, "header_size" => (int)$headers['Content-Length'], "saved_size" => (int)filesize($imgSavePath), "saved_path" => $imgSavePath ]; //spit out the JSON echo json_encode($apiResponse); exit(); ``` The JSON: ``` {"status":1,"message":"success","data":[{"mid":340052,"card_type":"kakusei","header_size":48337,"saved_size":48337,"saved_path":"..\/card\/kakusei\/340052.png"}]} ``` At first it seems valid. My Ajax that retrieves this PHP always ends with `parseerror` (thus going into the `error` part of `ajax()`). If you copy and paste this JSON on http://jsonlint.com/, it says "Unexpected token " and http://jsonformatter.curiousconcept.com/ says is not valid. I've tried `echo json_encode($apiResponse, JSON_UNESCAPED_SLASHES);` even though escaping slashes is ok `\/` but made no difference. But what isn't exactly valid? Wasn't PHP supposed to return valid JSON? Extra info: Testing on Windows7, Chrome v28.XX, using PHP 5.4.XX on Apache Questions I've read before actually posting this one: - json_encode creating malformed JSON data? - https://stackoverflow.com/a/15654848/684932 - about json_encode and ajax dataType: "json" - php json_encode not returning proper json encoded string Update: Copying from SO into JSONlint gives valid json. So I investigated a little further and noticed the PHP is creating a weird hidden character that is actually making json invalid. See below screenshot. How I fix that?