ajax nevrací data

$(document).ready(function() {
                
               $("#formbutton").click(function() {       
                   
                  $(this).removeClass("btn-primary");
                  $(this).addClass("btn-warning");
                  $(this).text("Loading...");
                  var text = $("<span></span>");
                  text.addClass("glyphicon glyphicon-refresh glyphicon-refresh-animate");
                  $(this).append(text);
                  
                  var myData = $("#vzkaz").val();
                  
                  jQuery.ajax({
                     type: "POST",
                     url: "index.php",
                     dataType: "text",
                     data: {content:myData},
                     contentType: 'application/x-www-form-urlencoded; charset=UTF-8',
                     
                     success:function(response) {
                         $("#vzkaz").val("");
                         text.removeClass("glyphicon glyphicon-refresh glyphicon-refresh-animate");
                         $("#formbutton").removeClass("btn-warning");
                         $("#formbutton").addClass("btn-primary");
                         $("#formbutton").text("Vložit příspěvek");
                     },
                     
                     error:function (xhr, ajaxOptions, thrownError) { 
                         alert(thrownError);
                     }        
                  });
                  
               });
            });

$server = "localhost";
$user = "root";
$pass = "root";
$db = "test";

$mysqli = new mysqli($server,$user,$pass,$db);


$data = $_POST["content"];

$result = $mysqli->query("INSERT INTO jquery (obsah) VALUES ('".$data."')");

if($result) {
    echo "tralalala";
    $mysqli->close();
} else {
        
        //header('HTTP/1.1 500 '.mysql_error()); //display sql errors.. must not output sql errors in live mode.
        header('HTTP/1.1 500 Looks like mysql error, could not insert record!');
        exit();
    }