Why would json_encode return an empty string

Question

I have a simple php structure with 3 nested arrays.

I do not use particular objects and I build myself the arrays with 2 nested loops.

Here is a sample of the var_dump of the array I want to convert to Json.

array (size=2)
  'tram B' => 
    array (size=2)
      0 => 
        array (size=3)
          'name' => string 'Ile Verte' (length=9)
          'distance' => int 298
          'stationID' => int 762
      1 => 
        array (size=3)
          'name' => string 'La Tronche Hôpital' (length=18)
          'distance' => int 425
          'stationID' => int 771
  16 => 
    array (size=4)
      0 => 
        array (size=3)
          'name' => string 'Bastille' (length=8)
          'distance' => int 531
          'stationID' => int 397
      1 => 
        array (size=3)
          'name' => string 'Xavier Jouvin' (length=13)
          'distance' => int 589
          'stationID' => int 438

In another script I have a similar structure and json_encode works fine. So I don't understand why json_encode won't work here.

Edit : there seems to be a problem with the encoding. When mb_detect_encoding returns ASCII, the json_encode works but when it returns UTF8, it doesn't work anymore.

Edit2 : json_last_error() returns JSON_ERROR_UTF8 which means : Malformed UTF-8 characters, possibly incorrectly encoded.

Answer 1

using utf8_encode() on those string solved my problem.

Answer 2

Adam Bubela also presented really good solution who helped me solved my problem, and here is the simplified function :

function utf8ize($d)
{ 
    if (is_array($d) || is_object($d))
        foreach ($d as &$v) $v = utf8ize($v);
    else
        return utf8_encode($d);

    return $d;
}

Answer 3

I was getting data from ob_get_clean() and had the same problem, but above solutions don't work for me. In my case solution was this, maybe it will help somebody.

$var = mb_convert_encoding($var, 'UTF-8');

Answer 4

Well after 2 hours of digging (cf Edits)

I found out following :

• In my case it's a encoding problem
• mb_detect_encoding returns probably a faulty response, some strings were probably not UTF-8
• using utf8_encode() on those string solved my problem.

Here is a recursive function that can force convert to UTF-8 all the strings contained in an array:

function utf8ize($d) {
    if (is_array($d)) {
        foreach ($d as $k => $v) {
            $d[$k] = utf8ize($v);
        }
    } else if (is_string ($d)) {
        return utf8_encode($d);
    }
    return $d;
}

Use it simply like this:

echo json_encode(utf8ize($data));

Answer 5

I have improved Adam Bubela's answer. I just hate it when blocks are not closed by { and }. It's cleaner and you don't introduce bugs or maybe it's that I did use Perl in the past :)

<?php

class App_Updater_String_Util {    
    /**
     * Usage: App_Updater_String_Util::utf8_encode( $data );
     *
     * @param mixed $d
     * @return mixed
     * @see http://stackoverflow.com/questions/19361282/why-would-json-encode-returns-an-empty-string
     */
    public static function utf8_encode($d) {
        if (is_array($d)) {
            foreach ($d as $k => $v) {
                $d[$k] = self::utf8_encode($v);
            }
        } elseif (is_object($d)) {
            foreach ($d as $k => $v) {
                $d->$k = self::utf8_encode($v);
            }
        } elseif (is_scalar($d)) {
            $d = utf8_encode($d);
        }

        return $d;
    }
}

?>

Answer 6

I ran into this issue on a server running an older version of PHP (5.2). I was using the JSON_FORCE_OBJECT flag, and apparently that isn't supported until 5.3

So if you're using that flag be sure to check your version!

A workaround appears to be just casting to an object before encoding, like:

json_encode((object)$myvar);