抓取查询，放入$ _Session

Question

Trying to get the value I'm setting at the end for $_SESSION to be the user_id from the query, and not $username. I can't seem to work my way around modifying the query. I'm sure this is crazy easy for some of the gurus here.

if(isset($_POST['login']))
{
    $username = mysqli_real_escape_string($conn,$_POST['username']);
    $pass = mysqli_real_escape_string($conn,$_POST['password']);
    $sel_user = "select user_id, user_first_name from users where username='$username' AND password='$pass'";
    $run_user = mysqli_query($conn, $sel_user);
    $check_user = mysqli_num_rows($run_user);

    if($check_user>0){
        $_SESSION['session_id']=$username;
    }
}

Answer 1

You need to read the row from the query results:

$row = mysqli_fetch_assoc($run_user);

Then you get the user_id from there:

if ($row) {
    $_SESSION['session_id'] = $row['user_id'];
}

You don't need to call mysqli_num_rows(). If there were no matches, mysqli_fetch_assoc() will return false.