new Chart(document.getElementById("line-chart"), {
  type: 'line',
  data: {
    labels: ['2018-10-01','2018-10-02','2018-10-03','2018-10-04','2018-10-05','2018-10-06','2018-10-07','2018-10-08','2018-10-09','2018-10-10','2018-10-11','2018-10-12','2018-10-13','2018-10-14','2018-10-15','2018-10-16','2018-10-17','2018-10-18','2018-10-19',],
    datasets: [{
        data: [181,221,222,209,266,649,725,434,249,232,176,271,418,354,189,154,202,187,222,],
        label: "Карпы",
        borderColor: "#3e95cd",
        fill: false
      },
      {
        data: [100,14,16,247],
        label: "Пескари",
        borderColor: "#333333",
        fill: false
      }
    ]
  }
});

$X_date="";
            $Y_du="";
                while($row = $STH->fetch()) {
                    $X_date.="'".$row['date']."',";
                    $Y_du.=$row['new_users_count'].",";
                    }

                        echo $data ;
        echo json_encode(array('X_date'=>$X_date, 'Y_dau'=>$Y_dau));

$.ajax({
          type: "POST",
          dataType:'json',
          url: "serverscript/output.php",
          success: function(json) {
            console.log(json.X_date);
            new Chart(document.getElementById("line-chart"), {
                  type: 'line',
                  data: {
                    labels: [json.X_date],
                    datasets: [{
                        data: [json.Y_dau],
                        label: "Карпы",
                        borderColor: "#3e95cd",
                        fill: false
                      }
                    ]
                  }
                })
          },
          error: function() {
            console.log("ERROR", this);
          }
        });

data: {
                        labels: [json.X_date],
                        datasets: [{
                            data: [json.Y_dau],
                            label: "Карпы",
                            borderColor: "#3e95cd",
                            fill: false
                          }

console.log("X_date"+json.X_date);
    console.log("Y_dau"+json.Y_dau);

X_date'2018-10-01','2018-10-02','2018-10-03','2018-10-04','2018-10-05','2018-10-06','2018-10-07','2018-10-08','2018-10-09','2018-10-10','2018-10-11','2018-10-12','2018-10-13','2018-10-14','2018-10-15','2018-10-16','2018-10-17','2018-10-18','2018-10-19',

Y_dau181,221,222,209,266,649,725,434,249,232,176,271,418,354,189,154,202,187,222,


console.log("json.X_date", typeof json.X_date, json.X_date);
console.log("json.Y_du", typeof json.Y_dau, json.Y_dau);

json.X_date string '2018-10-01','2018-10-02','2018-10-03','2018-10-04','2018-10-05','2018-10-06','2018-10-07','2018-10-08','2018-10-09','2018-10-10','2018-10-11','2018-10-12','2018-10-13','2018-10-14','2018-10-15','2018-10-16','2018-10-17','2018-10-18','2018-10-19',

json.Y_du string 181,221,222,209,266,649,725,434,249,232,176,271,418,354,189,154,202,187,222,

console.log("json.X_date", typeof json.X_date, json.X_date);
console.log("json.Y_dau", typeof json.Y_dau, json.Y_dau);