solved it. problem in values some values are not in collation utf-8. So i had convert it using function:
<pre lang="PHP">
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 $d;
}
and then echo json_encode(utf8ize($result))