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;