ionic application does not show Arabic text

im creating an Ionic Framework Application. i retrieve a set of database records through json format and display it on my ionic application. but my application page displays ????? for arabic characters

My db table enter image description here

I use json to retreive the records 

$query = "SET NAMES 'utf8'";
$query = "SET CHARACTER SET utf8";
$query = "select * from XXXX ";
$result = $mysqli->query($query) or die($mysqli->error.__LINE__);

$arr = array();
if($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        $arr[] = $row;  
    }
}
echo $json_response = json_encode($arr, JSON_UNESCAPED_UNICODE);

The json Output

[{"arabic_title":"???????","offer_type":"0"}]

In my ionic application i have used <meta http-equiv="Content-Type" content="application/json ; charset=utf-8" />

but i still don't get the arabic character