SQL已连接，但无法使用php运行查询

Question

    $host="43.42.157.14";
$port=3307;
$user="admin";
$password="password";
$dbname="test";

$con = new mysqli($host, $user, $password, $dbname, $port)
or die ('Could not connect to th e database server' . mysqli_connect_error());
if (!$con->connect_error) {
echo "connect successfully"."<br>";
}


$sql = "SELECT * FROM test.calls";
$result = $con->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo $row['id_call'];
    }
    } else {
        echo "0 results";
    }

执行此代码后，结果为“连接成功”和“ 0结果”；

在phpmyadmin中，sql查询有效！怎么了？