How do I validate my uid with the current session's uid in this code.
This is the page shown to users after they login to the website. Here they can register for events using their UserId. So how do I validate that?

Code:

```
    $error = array();
if (isset($_POST['uid'], $_POST['eventList']))
{
    if (empty($_POST['uid']))
        $error[] = 'Please Enter a name';
    else
    {
     $query = "INSERT INTO event (Memberid, events) VALUES (?, ?)";
     if ($stmt = mysqli_prepare($dbc, $query))
      {
        mysqli_stmt_bind_param($stmt, 'is', $_POST['uid'], $_POST['eventList']);
        mysqli_stmt_execute($stmt);
        mysqli_stmt_close($stmt);

        echo 'Success';
      }
    }
}

```

This is the List contents

```
Event Name: <select style="width:200px;" name="eventList" tabindex="5">

<form action="page.php" method=POST>
User ID: <input type="text" name="uid" id="uid"><br
<option value="select">Select Event</option>

<optgroup label="Specials">

<option value="Vogue">Vogue</option>

<option value="Raddrock">Raddrock</option>

<option value="Razzmatazz">Razzmatazz</option>

</optgroup>
</select><br>
<input type="submit" value="register">
</form>

```