Use mysqli_fetch_row(). Try this:

$query = "SELECT ssfullname, ssemail FROM userss WHERE user_id = ".$user_id;
$result = mysqli_query($conn, $query);
$row   = mysqli_fetch_row($result);

$ssfullname = $row['ssfullname'];
$ssemail    = $row['ssemail'];

When only one result is needed, there is no need to use a loop. Get the row directly.

• If you need to obtain the entire row of data as an associative array:

  $row = $result->fetch_assoc();

• If only one value is required, starting with PHP 8.2:

  $value = $result->fetch_column();

• Or for older versions:

  $value = $result->fetch_row()[0] ?? false;

Here are complete examples of different use cases

Variables used for query

When using variables in a query, prepared statements must be used. For example, let's say we have a variable $id:

PHP >= 8.2

// 获取单行数据
$sql = "SELECT fullname, email FROM users WHERE id=?";
$row = $conn->execute_query($query, [$id])->fetch_assoc();

// 如果只需要一个值
$sql = "SELECT count(*) FROM users WHERE id=?";
$count = $conn->execute_query($query, [$id])->fetch_column();

Older versions of PHP:

// 获取单行数据
$query = "SELECT fullname, email FROM users WHERE id=?";
$stmt = $conn->prepare($query);
$stmt->bind_param("s", $id);
$stmt->execute();
$result = $stmt->get_result();
$row = $result->fetch_assoc();

// 如果只需要一个值
$query = "SELECT count(*) FROM userss WHERE id=?";
$stmt = $conn->prepare($query);
$stmt->bind_param("s", $id);
$stmt->execute();
$result = $stmt->get_result();
$count = $result->fetch_row()[0] ?? false;

A detailed explanation of the above process can be found in my article . The reasons why this process must be followed are explained in this famous Question

There are no variables in the query

In your case, there are no variables to use in the query, you can use the query() method:

$query = "SELECT fullname, email FROM users ORDER BY ssid";
$result = $conn->query($query);
// 如果需要一个数组
$row = $result->fetch_assoc();
// 或者如果只需要一个值
$value = $result->fetch_row()[0] ?? false;