我已经尝试实现用户自动登录功能有一段时间了，但我并没有成功地让它工作。下面是我一直在尝试但没有成功的代码

<?php
$conn = mysqli_connect("localhost","username","password","friendzo_ne");

// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
  $expire = 365*24*3600; // We choose a one year duration
ini_set('session.gc_maxlifetime', $expire);
session_start();
setcookie(session_name(),session_id(),time()+$expire); 
if (isset($_SESSION['user_login'])){
$user = $_SESSION["user_login"];    
}
else
{
    "";
}
?>