<?php
ob_start();
$host="localhost"; // Host name
$username=""; // mysqli username
$password=""; // mysqli password
$db_name="test"; // Database name
$tbl_name="members"; // Table name

// Connect to server and select databse.
mysqli_connect("$host", "$username", "$password", "$db_name")or die("cannot connect");

// Define $myusername and $mypassword
$myusername=$_POST['myusername'];
$mypassword=$_POST['mypassword'];

// To protect mysqli injection (more detail about mysqli injection)
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysqli_real_escape_string($myusername);
$mypassword = mysqli_real_escape_string($mypassword);

$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result=mysqli_query($sql);

// mysqli_num_row is counting table row
$count=mysqli_num_rows($result);
// If result matched $myusername and $mypassword, table row must be 1 row

if($count==0){
// Register $myusername, $mypassword and redirect to file "login_success.php"
session_register("myusername");
session_register("mypassword");
header("location:login_success.php");
}
else {
echo "Wrong Username or Password";
}

ob_end_flush();
?>