I'm making an ajax call using jQuery as below.

$.ajax({

    type: POST,

    url: proc.php,

    dataType: 'json',

    data: dataString,

    cache: false,

    success: function(data){

        alert(data.vote[0].line);    //Where error shows

    }

});

The php page returns echo json_encode($string); which is like

{ 'vote' : [{ 'line' : 'newline1', 'up' : '0', 'down' : '1'},
{ 'line' : 'newline2', 'up' : '4', 'down' : '1'}
]}

When I run it, an error comes up saying

Uncaught TypeError: Cannot read property '0' of undefined on the line commented above in the ajax call

Can anyone help me point out where am I doing it wrong??

UPDATE:

the variable $string is generated as below

    $comma = ,;

    $success = mysql_query($query, $connection);

    while($row = mysql_fetch_array($success)){

            $voteUp = $row['voteup'];

            $voteDwn = $row['votedwn'];



            $vote .= $comma . { 'line' : '{$row['entryid']}', 'up' : '{$voteUp}', 'down' : '{$voteDwn}';

            $comma = ,;

        }

    $string = { 'vote' : [ . $vote . ]};

    echo json_encode($string);