json_encode problem - php

Question

This has got me completely stumped:
print_r($json);
echo json_encode($json);
output:
Array
(
[query] => dia
[suggestions] => Array
(
[0] => Diana Johnson
[1] => Diane Abbott
)
)
{"query":"dia","suggestions":[null,null]}
What on earth is going wrong?
edit Just to add to the general wtf-ery of this, here's another sample:
Array
(
[query] => david
[suggestions] => Array
(
[0] => David Cameron
[1] => David Amess
[2] => David Anderson
[3] => David Blunkett
[4] => David Burrowes
)
)
{"query":"david","suggestions":["David Cameron",null,null,null,null]}

Answer 1

I'm posting this as an answer because I need the full formatting abilities of the normal answer box.
Yeah, it's UTF-8 all right. From the PHP interactive prompt:
php > $david = urldecode('David%A0Amess');
php > echo json_encode($david);
null
php > $david = urldecode('David%20Amess');
php > echo json_encode($david);
"David Amess"
php > $david = urldecode('David%c2%a0Amess');
php > echo json_encode($david);
"David\u00a0Amess"
So, we can assume that you're dealing with either ISO-8859 or Windows-1252, given that we're dealing with a broken NBSP. We can fix this with iconv:
php > $david = urldecode('David%A0Amess');
php > $david_converted = iconv('Windows-1252', 'UTF-8', $david);
php > echo json_encode($david_converted);
"David\u00a0Amess"
So, this means that you are going to need to not trust what you're pulling out of MySQL, assuming you've done the SET NAMES thing. Clearly something has gone awry when you were inserting data. You probably weren't giving MySQL well-formed UTF-8, and it stupidly did not complain. (If you were using other, smarter, more correct databases, and tried to insert the unencoded NBSP, they would have rejected the input.)

Answer 2

This looks like an autocomplete script. I assume your results are loaded from a database, are you sure they're utf-8? If you cannot replicate this functionality by hardcoding the array, then it's probably an encoding issue.
According to http://php.net/manual/en/function.json-encode.php, "This function only works with UTF-8 encoded data."
You can also use http://php.net/manual/en/function.json-last-error.php to see the last error.