php - mysql ระบบ login มีปันหาคับ ช่วยเช็คโค้ดไห้ที งง มากๆ คับ

<?php
session_start(); 

$host="studb";
$username="sr"; 
$password="gir"; 
$db_name="mdb"; 
$tbl_name="users";

// Connect to server and select databse.
	mysql_connect("studb","sr","gir");
	mysql_select_db("mdb");

$username=$_POST['username'];
$password=$_POST['password'];

$encrypt_password = md5($password);

$sql="SELECT * FROM $tbl_name WHERE username='$username' and password='$encrypt_password'";
$result=mysql_query($sql);

$count=mysql_num_rows($result);


if($count==1){

// Register $myusername, $mypassword and redirect to file "login_success.php"
$_SESSION['username']=$_POST['username'];
$_SESSION['$encrypt_password']=$_POST['$encrypt_password'];
$_SESSION['status']=$_GET['status'];

session_write_close();
			
	if($objResult["status"] == "activated")
	{
header("location:memberU.php");
}}

else {
echo "Wrong Username or Password";
}
?>