<?php
session_start(); //starts a session
$con = mysql_connect("localhost","username","password"); //saves the connection details to a variable
if (!$con) //tests if the conection isnt made
  {
  die('Could not connect: ' . mysql_error()); // kills the connection and prints the error
  }

mysql_select_db("hostafile", $con); // selects the database using this login details ($con)

list($login) = mysql_fetch_row(mysql_query("SELECT COUNT( *) FROM users WHERE username = '".$_POST['username']."' AND password = '".$_POST['password']."'")); //checks through the database for the matchign login detals.
echo mysql_error(); //if there is a error this show it
if( $login=='1') //tests if the check finds one correct match
{
$loginname=$_POST["username"]; //saves the login name to a variable
$_SESSION['login']=$loginname; // creates a session that shows they are logged in
print("<script language = 'javascript'>alert('You have been logged in');window.location='index.php';</script>"); // shows a javascript pop up saying they have been logged in
}
else
echo "sorry we where unable to log you in"; // if no matches where found a message is shown saying so.

mysql_close($con) // closes the connection to the database
?>