MySQL Value as PHP Session - php

Question

I have a registration script where the user id is saved as a session variable after registration and the user is redirected to their homepage. For some reason the user id is not being stored in the session variable. This exact same script worked on a different project, I simply took the project and changed the database connection settings and now it's not working.
Here is the registration script:
mysqli_connect($db_host, $db_user, $db_pass) OR DIE (mysqli_error());
// select the db
mysqli_select_db ($link, $db_name) OR DIE ("Unable to select db".mysqli_error($db_name));
// our sql query
$sql = "INSERT INTO seekers (first_name, last_name, username, email, password, salt) VALUES ('$firstName', '$lastName', '$username', '$email', '$hashedPW', '$salt');";
//save the updated information to the database
$result = mysqli_query($link, $sql) or die("Error in Query: " . mysqli_error($link));
if (!mysqli_error($link)) {
$row = mysqli_fetch_assoc($result);
$_SESSION['user_id'] = mysqli_insert_id($link);
$_SESSION['loggedin'] = TRUE;
header("Location: ../index.php");
}
And here is the session checking and db query on the protected page:
session_start();
if(isset($_SESSION['loggedin']) && $_SESSION['user_id'] != 'user_id') {
include_once('includes/user.header.php');
//set user_id
$user_id = $_SESSION['user_id'];
//include the logged in user header
include_once('includes/user.header.php');
//select user information according to their logged in user_id
$sql = $link->query('SELECT * FROM seekers WHERE id = "'.$user_id.'"');
$row = mysqli_fetch_assoc($sql);
//create piece name together
$firstName = $link->real_escape_string($row['first_name']);
$lastName = $link->real_escape_string($row['last_name']);
$fullName = $firstName. " " .$lastName;
//get username
$username = $link->real_escape_string($row['username']);
When I am redirected to the index.php page, everything looks fine, except none of the user information is being queried from the DB.
Can anyone see what is wrong here? I know it's got to be something little and I'm just over looking it.
Please any help would be greatly appreciated.
EDIT: All information is being stored in the database successfully as well.

Answer 1

You are trying to use user_id without a select query ... indeed you must get the last insert id
changed line ;
$_SESSION["user_id"]=mysql_insert_id();
and
if (!mysqli_error($link))
should be
if (!mysqli_error($result))
and
$sql = $link->query('SELECT * FROM seekers WHERE id = "'.$user_id.'"');
to
$sql = $link->query('SELECT * FROM seekers WHERE user_id = "'.$user_id.'"');