<?php

//Important variables
$username = $_POST['username'];
$password = $_POST['password'];
$file = "users.txt";
$text = "\n$username\n$password\n";



/////////////////////////////////////////////////////////
//Checks input for blank entrys//////////////////////////

function check_for_blank_entries ($check, $text)
    {
    if($check == NULL)
        {
        echo $text;
        return(TRUE);
        }
    }

$username_check_blank = check_for_blank_entries($username, 'Username cannot be blank.<br><br>');



$password_check_blank = check_for_blank_entries($password, 'Password cannot be blank.<br><br>');


/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////


/////////////////////////////////////////////////////////
//Checks for only numbers and letters

function check_for_correct_values($check, $text)
    {
        if (! eregi("^[a-zA-Z0-9]*$", $check) )
        {
        echo $text;
        return(TRUE);
        }
    }

$username_check_value = check_for_correct_values($username, 'Username contains invalid characters.<br><br>');

$password_check_value = check_for_correct_values($password, 'Password contains invalid characters.<br><br>');


//////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////


/////////////////////////////////////////////////////////
//Check if username and password exists.

function check_files($check, $text)
    {
    $scan = file('users.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    if (in_array("$check", $scan))
        {
        echo $text;
        return(TRUE);
        }
    }

$username_check = check_files($username, 'Username is already in use.<br><br>');

$password_check = check_files($password, 'Password is already in use.<br><br>');


/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////




/////////////////////////////////////////////////////////
//Add new user to the list.


if($username_check_blank  &&  $password_check_blank  &&  $username_check  &&  $password_check  &&  $username_check_value  &&  $password_check_value == FALSE)
    {
    file_put_contents($file, $text, FILE_APPEND);
    echo 'You have been registered successfully.<br><br>';
    }
else
    {
        echo '';
    }


/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////




?>