para un login script, es necesario comparar el valor de $_SESSION?

[webankenovi]

function login_user ($email, $password) {
global $dbc;
$query= "select count(email) as user, user_id from users where email='$email'and password='$password';";
$result= mysqli_query($dbc, $query);
$row = mysqli_fetch_array($result);
if( $row['user']==1) {
$token= uniqid(rand(),false);
$query= "update users set token='$token' where user_id='".$row['user_id']."'";
$result=mysqli_query($dbc, $query);

if($result){
$_SESSION['token'] = $token;
}


}
}
login_user($email, $password);