How can I get an unknown username given an ID?

Question

I got a numerical ID of 20 characters witch looks like 10527391670258314752, given this ID, how can I get the username associated with it?

The table looks like this:

id                   | name | password | balance   
10527391670258314752 | Jhon | 12345    | 12.51

The username retrieved from the database should then be stored into $_SESSION['name'].

I've tried this:

$connection = mysqli_connect('localhost', 'root', '', 'user_data');
$id = '10527391670258314752';

$query = "SELECT username FROM user_data WHERE id = '$id'";
$result = mysqli_query($connection, $query);

$record = mysqli_fetch_array($id);
$_SESSION['id'] = $record;

echo $_SESSION['id'];

The output is Array() instead of the name.

Answer 1

That's actually a very good question that has almost no good answers on Stack Overflow.

Basically you need the following steps to perform a SELECT query using mysqli:

• create a correct SQL SELECT statement and replace all variables in the query with with question marks (called placeholders or parameters)
• Prepare the resulting query
• Bind all variables to the previously prepared statement
• Execute the statement
• get the mysqli result variable from the statement.
• fetch your data

The detailed explanation can be found in my article, How to run a SELECT query using Mysqli, as well a helper function to simplify the routine.

Following this plan here is your code

$sql = "SELECT * FROM users WHERE id=?"; // SQL with parameters
$stmt = $conn->prepare($sql); 
$stmt->bind_param("s", $id);
$Stmt->execute();
$result = $stmt->get_result(); // get the mysqli result
$user = $result->fetch_assoc(); // fetch the data 

now you can store the username in the session variable:

$_SESSION['name'] = $user['name'];