为什么我的php没有返回正确的json？ （“期待UTF-8，UTF-16或UTF-32”）

Question

I am having trouble using Alamofire in iOS because because my php seems to not be returning valid json. I have added the header "header("Content-Type: application/json; charset=utf-8");" before encoding array but it still does not work. If it matters some columns in my database table are encoding using utf8mb4_unicode_ci. Here is my php:

<?php
    $con = mysqli_connect("localhost","hide","hide","hide");
    mysqli_set_charset($con, "utf8");

    if(mysqli_connect_errno())
    {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }

    $sql = "SELECT * FROM Business";

    if($result = mysqli_query($con, $sql))
    {
        $resultArray = array();
        $tempArray = array();

        while($row = $result->fetch_object())
        {
            $tempArray = $row;
            array_push($resultArray, $tempArray);
        }

        header("Content-Type: application/json; charset=utf-8");
        echo json_encode($resultArray);
    }

    mysqli_close($result);
    mysqli_close($con);
?>

Unformatted json:

[{"business_id":"0","imageURL":"imageUrl","shortDescription":"shortDescription","longDescription":"longDescription","price":"price","specialText":"specialText","order_rank":"1"}]

Here is formatted json specifying error: