<?php
include "config/koneksi.php";
$pass=md5($_POST['password']);
$level=$_POST['level'];
$username = $_POST['id_user'];
if ($level=='Admin')
{
$login=mysql_query("SELECT * FROM rb_users
			WHERE email='".mysql_real_escape_string($username)."' AND password='$pass' AND level='$level'");
$cocok=mysql_num_rows($login);
$r=mysql_fetch_array($login);
 
if ($cocok > 0){
	session_start();
	session_register("SES_ADMIN");
	$_SESSION[id_user]     = $r[id_user];
	$_SESSION[namauser]     = $r[username];
	$_SESSION[email]    	= $r[email];
  	$_SESSION[namalengkap]  = $r[nama_lengkap];
  	$_SESSION[passuser]     = $r[password];
  	$_SESSION[leveluser]    = $r[level];
 
	header('location:admin/media.php?module=home');
	}
else {
echo "<script>window.alert('Username atau Password anda salah.');
				window.location='administrator.php'</script>";
	}
}
 
else if ($level=='Member')
{
$login=mysql_query("SELECT * FROM rb_users
			WHERE email='".mysql_real_escape_string($username)."' AND password='$pass' AND level='$level'");
$cocok=mysql_num_rows($login);
$r=mysql_fetch_array($login);
 
if ($cocok > 0){
	session_start();
	session_register("SES_MEMBER");
	$_SESSION[id_user]     = $r[id_user];
	$_SESSION[passuser]     = $r[password];
  	$_SESSION[namalengkap]  = $r[nama_lengkap];
	$_SESSION[email]    	= $r[email];
	$_SESSION[telp]    		= $r[no_telp];
	$_SESSION[alamat]    	= $r[alamat_lengkap];
	$_SESSION[umur]   	 	= $r[umur];
  	$_SESSION[leveluser]    = $r[level];
 
	header('location:member');
	}
else {
echo "<script>window.alert('Username atau Password anda salah.');
				window.location='login.html'</script>";
	}
}
 
?>
 
 
yang seharusnya gmna kalau php versi if 5.4 > yaa ? mohon infonya
error di  bagian
 
Notice: Undefined index: password in C:\xampp\htdocs\pa\cek_login.php on line 4
 
Notice: Undefined index: level in C:\xampp\htdocs\pa\cek_login.php on line 5
 
Notice: Undefined index: id_user in C:\xampp\htdocs\pa\cek_login.php on line 6

Assalam, disini sudah kita infokan cara untuk mengatasinya mas,.. :)
#https://members.phpmu.com/forum/read/share-banyak-ditemukan-error-pada-beberapa-aplikasi