You're problem seems to stem from the fact that you're creating a multi-dimensional array. You're pushing an array as an element of the existing $results array. For you're desired output, $results should be an associative array, not an array of associative arrays.
Provided there is only one row in your result set, try this instead:
// Remove the while loop if you're only returning a single row
// such as with a LIMIT = 1 clause in your SQL statement.
$row = mysqli_fetch_array($sql);
// Push the single row as an array into $result
$results = array(
'wdatatype' => $row['wdatatype'],
'wdb' => $row['wdb'],
'wbyte' => $row['wbyte'],
'wbit' => $row['wbit'],
'bitval' => $row['bitval'],
);
// Now echo the json_encode
echo json_encode($results);
When converted using json_encode, the above will turn into a single object like so:
{"wdatatype":"DB","wdb":"100","wbyte":"0","wbit":"0","bitval":"1"}
rather than an array of objects.
Note: As @PankajGarg and @AmalMurali pointed out this should be used if you're only returning a single row. Failing to remove the while loop and returning a result set of more than one row will yield you a return of the last row only.
For a result set containing multiple rows, your current structure will work perfectly.
Alternatively as @Nilpo pointed out, you can simplify the above process by using mysqli_fetch_assoc() to return an associative array for you.
$row = mysqli_fetch_assoc($sql);
// Now echo the json_encode
echo json_encode($row);
