<?php
//This checks for required fields from the form.
if ((!$_POST[username]) || (!$_POST[password]))
{
header("Location: P4 LoginForm.php");
exit;
}

//This reads values from the form.
$form_user = $_POST[username];
$form_password = $_POST[password];

$flag = FALSE;
$filename = "users.txt";
$fp = fopen( $filename, "r" ) or die ("Couldn't open $filename");

while ( ! feof( $fp ) ) {
$line = fgets( $fp);
$user = strtok($line, ","); //Username
$password = strtok(","); //Password
if (($form_user == $user) && ($form_password == $password))
{
$flag = TRUE;
}
break;
}

if ($flag)
{
echo "<br>Congratulations, you're logged in";
}

else{
$filename = "users.txt";
$updateuser = $_POST ['username'];
$updatepass = $_POST ['password'];

$fp = fopen( $filename, "a" ) or die("Couldn't open $filename");
fwrite( $fp, "$updateuser,$updatepass\n") or die ("Couldn't write values to your file!");
fclose( $fp );
echo "<br>An account has been created for you!";
}
?>