Coba

<?php
$sambung=mysqli_connect("localhost","root","","login");
$user=$_POST['user'];
$pass=$_POST['password'];
$cari=mysqli_query($sambung,"select * from login_admin where user_name='$user' and user_pass='$pass'") or die ("Gagal");
$lihat=mysqli_num_rows($cari);
if (isset($_POST['submit']))
{
if (empty($user) and empty($pass))
{
	echo "User name dan Password tidak boleh kosong";
}
elseif ($lihat<1) {
	echo "Username dan Password Salah";
}
else
{
session_start();
$_SESSION['password']=$pass;
header("location:admin.php");
}
}
?>