session.php

<?
/**************************/
// Constants
/**************************/

/**
 * Database Constants - these constants are required
 * in order for there to be a successful connection
 * to the MySQL database. Make sure the information is
 * correct.
 */
define("DB_SERVER", "<SERVER>");
define("DB_NAME", "<DATABASE>");

// Session User
define("DB_USER", "<USERNAME>");
define("DB_PASS", "<PASSWORD>");

/**
 * Database Table Constants - these constants
 * hold the names of all the database tables used
 * in the script.
 */
define("TBL_USERS", "users");
define("TBL_ACTIVE_USERS",  "active_users");
define("TBL_ACTIVE_GUESTS", "active_guests");
define("TBL_BANNED_USERS",  "banned_users");

/**
 * Special Names and Level Constants - the admin
 * page will only be accessible to the user with
 * the admin name and also to those users at the
 * admin user level. Feel free to change the names
 * and level constants as you see fit, you may
 * also add additional level specifications.
 * Levels must be digits between 0-9.
 */
define("ADMIN_NAME", "<ADMIN_USER>");
define("GUEST_NAME", "Guest");
define("ADMIN_LEVEL", 9);
define("USER_LEVEL",  1);
define("GUEST_LEVEL", 0);

/**
 * This boolean constant controls whether or
 * not the script keeps track of active users
 * and active guests who are visiting the site.
 */
define("TRACK_VISITORS", false);

/**
 * Timeout Constants - these constants refer to
 * the maximum amount of time (in minutes) after
 * their last page fresh that a user and guest
 * are still considered active visitors.
 */
define("USER_TIMEOUT", 5);
define("GUEST_TIMEOUT", 2);

/**
 * Cookie Constants - these are the parameters
 * to the setcookie function call, change them
 * if necessary to fit your website. If you need
 * help, visit www.php.net for more info.
 * <http://www.php.net/manual/en/function.setcookie.php>
 */
define("COOKIE_EXPIRE", 60*60*24*100);  //100 days by default
define("COOKIE_PATH", "/");  //Avaible in whole domain

/**
 * Email Constants - these specify what goes in
 * the from field in the emails that the script
 * sends to users, and whether to send a
 * welcome email to newly registered users.
 */
define("EMAIL_FROM_NAME", "NCANE.COM Admin");
define("EMAIL_FROM_ADDR", "noreply@ncane.com");
define("EMAIL_WELCOME", true);

/**
 * This constant forces all users to have
 * lowercase usernames, capital letters are
 * converted automatically.
 */
define("ALL_LOWERCASE", true);

/**************************/
// Database
/**************************/

class MySQLDB
{
   var $connection;         //The MySQL database connection
   var $connectionInsert;   //The MySQL database connection
   var $connectionUpdate;   //The MySQL database connection
   var $num_active_users;   //Number of active users viewing site
   var $num_active_guests;  //Number of active guests viewing site
   var $num_members;        //Number of signed-up users
   /* Note: call getNumMembers() to access $num_members! */

   // function to pick random connection username
	function RandomConnectionString()
	{
		return $randint;
	}

   /* Class constructor */
   function MySQLDB()
   {
	$this->connection = mysql_connect(DB_SERVER, DB_USER, DB_PASS) or die(mysql_error());
	mysql_select_db(DB_NAME, $this->connection) or die(mysql_error());

      /**
       * Only query database to find out number of members
       * when getNumMembers() is called for the first time,
       * until then, default value set.
       */
      $this->num_members = -1;
      
      if(TRACK_VISITORS){
         /* Calculate number of users at site */
         $this->calcNumActiveUsers();
      
         /* Calculate number of guests at site */
         $this->calcNumActiveGuests();
      }
   }

   /**
    * confirmUserPass - Checks whether or not the given
    * username is in the database, if so it checks if the
    * given password is the same password in the database
    * for that user. If the user doesn't exist or if the
    * passwords don't match up, it returns an error code
    * (1 or 2). On success it returns 0.
    */
   function confirmUserPass($username, $password){
      /* Add slashes if necessary (for query) */
      if(!get_magic_quotes_gpc()) {
	      $username = addslashes($username);
      }

      /* Verify that user is in database */
      $q = "SELECT password FROM ".TBL_USERS." WHERE username = '$username'";
      $result = mysql_query($q, $this->connection);
      if(!$result || (mysql_numrows($result) < 1)){
         return 1; //Indicates username failure
      }

      /* Retrieve password from result, strip slashes */
      $dbarray = mysql_fetch_array($result);
      $dbarray['password'] = stripslashes($dbarray['password']);
      $password = stripslashes($password);

      /* Validate that password is correct */
      if($password == $dbarray['password']){
         return 0; //Success! Username and password confirmed
      }
      else{
         return 2; //Indicates password failure
      }
   }
   
   /**
    * confirmUserID - Checks whether or not the given
    * username is in the database, if so it checks if the
    * given userid is the same userid in the database
    * for that user. If the user doesn't exist or if the
    * userids don't match up, it returns an error code
    * (1 or 2). On success it returns 0.
    */
   function confirmUserID($username, $userid){
      /* Add slashes if necessary (for query) */
      if(!get_magic_quotes_gpc()) {
	      $username = addslashes($username);
      }

      /* Verify that user is in database */
      $q = "SELECT userid FROM ".TBL_USERS." WHERE username = '$username'";
      $result = mysql_query($q, $this->connection);
      if(!$result || (mysql_numrows($result) < 1)){
         return 1; //Indicates username failure
      }

      /* Retrieve userid from result, strip slashes */
      $dbarray = mysql_fetch_array($result);
      $dbarray['userid'] = stripslashes($dbarray['userid']);
      $userid = stripslashes($userid);

      /* Validate that userid is correct */
      if($userid == $dbarray['userid']){
         return 0; //Success! Username and userid confirmed
      }
      else{
         return 2; //Indicates userid invalid
      }
   }
   
   /**
    * usernameTaken - Returns true if the username has
    * been taken by another user, false otherwise.
    */
   function usernameTaken($username){
      if(!get_magic_quotes_gpc()){
         $username = addslashes($username);
      }
      $q = "SELECT username FROM ".TBL_USERS." WHERE username = '$username'";
      $result = mysql_query($q, $this->connection);
      return (mysql_numrows($result) > 0);
   }
   
   /**
    * usernameBanned - Returns true if the username has
    * been banned by the administrator.
    */
   function usernameBanned($username){
      if(!get_magic_quotes_gpc()){
         $username = addslashes($username);
      }
      $q = "SELECT username FROM ".TBL_BANNED_USERS." WHERE username = '$username'";
      $result = mysql_query($q, $this->connection);
      return (mysql_numrows($result) > 0);
   }
   
   /**
    * addNewUser - Inserts the given (username, password, email)
    * info into the database. Appropriate user level is set.
    * Returns true on success, false otherwise.
    */
   function addNewUser($username, $password, $email){
      $time = time();
      /* If admin sign up, give admin user level */
      if(strcasecmp($username, ADMIN_NAME) == 0){
         $ulevel = ADMIN_LEVEL;
      }else{
         $ulevel = USER_LEVEL;
      }
      $q = "INSERT INTO ".TBL_USERS." VALUES ('$username', '$password', '0', $ulevel, '$email', $time)";
      return mysql_query($q, $this->connection);
   }
   
   /**
    * updateUserField - Updates a field, specified by the field
    * parameter, in the user's row of the database.
    */
   function updateUserField($username, $field, $value){
      $q = "UPDATE ".TBL_USERS." SET ".$field." = '$value' WHERE username = '$username'";
      return mysql_query($q, $this->connection);
   }
   
   /**
    * getUserInfo - Returns the result array from a mysql
    * query asking for all information stored regarding
    * the given username. If query fails, NULL is returned.
    */
   function getUserInfo($username){
      $q = "SELECT * FROM ".TBL_USERS." WHERE username = '$username'";
      $result = mysql_query($q, $this->connection);
      /* Error occurred, return given name by default */
      if(!$result || (mysql_numrows($result) < 1)){
         return NULL;
      }
      /* Return result array */
      $dbarray = mysql_fetch_array($result);
      return $dbarray;
   }
   
   /**
    * getNumMembers - Returns the number of signed-up users
    * of the website, banned members not included. The first
    * time the function is called on page load, the database
    * is queried, on subsequent calls, the stored result
    * is returned. This is to improve efficiency, effectively
    * not querying the database when no call is made.
    */
   function getNumMembers(){
      if($this->num_members < 0){
         $q = "SELECT * FROM ".TBL_USERS;
         $result = mysql_query($q, $this->connection);
         $this->num_members = mysql_numrows($result);
      }
      return $this->num_members;
   }
   
   /**
    * calcNumActiveUsers - Finds out how many active users
    * are viewing site and sets class variable accordingly.
    */
   function calcNumActiveUsers(){
      /* Calculate number of users at site */
      $q = "SELECT * FROM ".TBL_ACTIVE_USERS;
      $result = mysql_query($q, $this->connection);
      $this->num_active_users = mysql_numrows($result);
   }
   
   /**
    * calcNumActiveGuests - Finds out how many active guests
    * are viewing site and sets class variable accordingly.
    */
   function calcNumActiveGuests(){
      /* Calculate number of guests at site */
      $q = "SELECT * FROM ".TBL_ACTIVE_GUESTS;
      $result = mysql_query($q, $this->connection);
      $this->num_active_guests = mysql_numrows($result);
   }
   
   /**
    * addActiveUser - Updates username's last active timestamp
    * in the database, and also adds him to the table of
    * active users, or updates timestamp if already there.
    */
   function addActiveUser($username, $time){
      $q = "UPDATE ".TBL_USERS." SET timestamp = '$time' WHERE username = '$username'";
      mysql_query($q, $this->connection);
      
      if(!TRACK_VISITORS) return;
      $q = "REPLACE INTO ".TBL_ACTIVE_USERS." VALUES ('$username', '$time')";
      mysql_query($q, $this->connection);
      $this->calcNumActiveUsers();
   }
   
   /* addActiveGuest - Adds guest to active guests table */
   function addActiveGuest($ip, $time){
      if(!TRACK_VISITORS) return;
      $q = "REPLACE INTO ".TBL_ACTIVE_GUESTS." VALUES ('$ip', '$time')";
      mysql_query($q, $this->connection);
      $this->calcNumActiveGuests();
   }
   
   /* These functions are self explanatory, no need for comments */
   
   /* removeActiveUser */
   function removeActiveUser($username){
      if(!TRACK_VISITORS) return;
      $q = "DELETE FROM ".TBL_ACTIVE_USERS." WHERE username = '$username'";
      mysql_query($q, $this->connection);
      $this->calcNumActiveUsers();
   }
   
   /* removeActiveGuest */
   function removeActiveGuest($ip){
      if(!TRACK_VISITORS) return;
      $q = "DELETE FROM ".TBL_ACTIVE_GUESTS." WHERE ip = '$ip'";
      mysql_query($q, $this->connection);
      $this->calcNumActiveGuests();
   }
   
   /* removeInactiveUsers */
   function removeInactiveUsers(){
      if(!TRACK_VISITORS) return;
      $timeout = time()-USER_TIMEOUT*60;
      $q = "DELETE FROM ".TBL_ACTIVE_USERS." WHERE timestamp < $timeout";
      mysql_query($q, $this->connection);
      $this->calcNumActiveUsers();
   }

   /* removeInactiveGuests */
   function removeInactiveGuests(){
      if(!TRACK_VISITORS) return;
      $timeout = time()-GUEST_TIMEOUT*60;
      $q = "DELETE FROM ".TBL_ACTIVE_GUESTS." WHERE timestamp < $timeout";
      mysql_query($q, $this->connection);
      $this->calcNumActiveGuests();
   }
   
   /**
    * query - Performs the given query on the database and
    * returns the result, which may be false, true or a
    * resource identifier.
    */
   function query($query){
      return mysql_query($query, $this->connection);
   }
};

/* Create database connection */
$database = new MySQLDB;

/**************************/
// Session
/**************************/

class Session
{
   var $username;     //Username given on sign-up
   var $userid;       //Random value generated on current login
   var $userlevel;    //The level to which the user pertains
   var $time;         //Time user was last active (page loaded)
   var $logged_in;    //True if user is logged in, false otherwise
   var $userinfo = array();  //The array holding all user info
   var $url;          //The page url current being viewed
   var $referrer;     //Last recorded site page viewed
   /**
    * Note: referrer should really only be considered the actual
    * page referrer in process.php, any other time it may be
    * inaccurate.
    */

   /* Class constructor */
   function Session(){
      $this->time = time();
      $this->startSession();
   }

   /**
    * startSession - Performs all the actions necessary to 
    * initialize this session object. Tries to determine if the
    * the user has logged in already, and sets the variables 
    * accordingly. Also takes advantage of this page load to
    * update the active visitors tables.
    */
   function startSession(){
      global $database;  //The database connection
      session_start();   //Tell PHP to start the session

      /* Determine if user is logged in */
      $this->logged_in = $this->checkLogin();

      /**
       * Set guest value to users not logged in, and update
       * active guests table accordingly.
       */
	   
      if(!$this->logged_in){
         $this->username = $_SESSION['username'] = GUEST_NAME;
         $this->userlevel = GUEST_LEVEL;
         $database->addActiveGuest($_SERVER['REMOTE_ADDR'], $this->time);
      }
      /* Update users last active timestamp */
      else{
         $database->addActiveUser($this->username, $this->time);
      }
      
      /* Remove inactive visitors from database */
      $database->removeInactiveUsers();
      $database->removeInactiveGuests();
      
      /* Set referrer page */
      if(isset($_SESSION['url'])){
         $this->referrer = $_SESSION['url'];
      }else{
         $this->referrer = "/";
      }

      /* Set current url */
      $this->url = $_SESSION['url'] = $_SERVER['PHP_SELF'];
   }

   /**
    * checkLogin - Checks if the user has already previously
    * logged in, and a session with the user has already been
    * established. Also checks to see if user has been remembered.
    * If so, the database is queried to make sure of the user's 
    * authenticity. Returns true if the user has logged in.
    */
   function checkLogin(){
      global $database;  //The database connection
      /* Check if user has been remembered */
      if(isset($_COOKIE['cookname']) && isset($_COOKIE['cookid'])){
         $this->username = $_SESSION['username'] = $_COOKIE['cookname'];
         $this->userid   = $_SESSION['userid']   = $_COOKIE['cookid'];
      }

      /* Username and userid have been set and not guest */
      if(isset($_SESSION['username']) && isset($_SESSION['userid']) &&
         $_SESSION['username'] != GUEST_NAME){
         /* Confirm that username and userid are valid */
         if($database->confirmUserID($_SESSION['username'], $_SESSION['userid']) != 0){
            /* Variables are incorrect, user not logged in */
            unset($_SESSION['username']);
            unset($_SESSION['userid']);
            return false;
         }

         /* User is logged in, set class variables */
         $this->userinfo  = $database->getUserInfo($_SESSION['username']);
         $this->username  = $this->userinfo['username'];
         $this->userid    = $this->userinfo['userid'];
         $this->userlevel = $this->userinfo['userlevel'];
         return true;
      }
      /* User not logged in */
      else{
         return false;
      }
   }

   /**
    * login - The user has submitted his username and password
    * through the login form, this function checks the authenticity
    * of that information in the database and creates the session.
    * Effectively logging in the user if all goes well.
    */
   function login($subuser, $subpass, $subremember){
      global $database, $form;  //The database and form object
	  
      /* Username error checking */
      $field = "user";  //Use field name for username
      if(!$subuser || strlen($subuser = trim($subuser)) == 0){
         $form->setError($field, "* Username and/or password incorrect");
      }
      else{
         /* Check if username is not alphanumeric */
         if(!eregi("^([0-9a-z])*$", $subuser)){
            $form->setError($field, "* Username not alphanumeric");
         }
      }

      /* Password error checking */
      $field = "pass";  //Use field name for password
      if(!$subpass){
         $form->setError($field, "* Username and/or password incorrect");
      }
      
      /* Return if form errors exist */
      if($form->num_errors > 0){
         return false;
      }

      /* Checks that username is in database and password is correct */
      $subuser = stripslashes($subuser);
      $result = $database->confirmUserPass($subuser, md5($subpass));

      /* Check error codes */
      if($result > 0){
         $field = "user";
         $form->setError($field, "* Username and/or password incorrect");
      }
      //else if($result == 2){
      //   $field = "pass";
      //   $form->setError($field, "* Username and/or password incorrect");
      //}
      
      /* Return if form errors exist */
      if($form->num_errors > 0){
         return false;
      }

      /* Username and password correct, register session variables */
      $this->userinfo  = $database->getUserInfo($subuser);
      $this->username  = $_SESSION['username'] = $this->userinfo['username'];
      $this->userid    = $_SESSION['userid']   = $this->generateRandID();
      $this->userlevel = $this->userinfo['userlevel'];
      
      /* Insert userid into database and update active users table */
      $database->updateUserField($this->username, "userid", $this->userid);
      $database->addActiveUser($this->username, $this->time);
      $database->removeActiveGuest($_SERVER['REMOTE_ADDR']);

      /**
       * This is the cool part: the user has requested that we remember that
       * he's logged in, so we set two cookies. One to hold his username,
       * and one to hold his random value userid. It expires by the time
       * specified in constants.php. Now, next time he comes to our site, we will
       * log him in automatically, but only if he didn't log out before he left.
       */
      if($subremember){
         setcookie("cookname", $this->username, time()+COOKIE_EXPIRE, COOKIE_PATH);
         setcookie("cookid",   $this->userid,   time()+COOKIE_EXPIRE, COOKIE_PATH);
      }

      /* Login completed successfully */
      return true;
   }

   /**
    * logout - Gets called when the user wants to be logged out of the
    * website. It deletes any cookies that were stored on the users
    * computer as a result of him wanting to be remembered, and also
    * unsets session variables and demotes his user level to guest.
    */
   function logout(){
      global $database;  //The database connection
      /**
       * Delete cookies - the time must be in the past,
       * so just negate what you added when creating the
       * cookie.
       */
      if(isset($_COOKIE['cookname']) && isset($_COOKIE['cookid'])){
         setcookie("cookname", "", time()-COOKIE_EXPIRE, COOKIE_PATH);
         setcookie("cookid",   "", time()-COOKIE_EXPIRE, COOKIE_PATH);
      }

      /* Unset PHP session variables */
      unset($_SESSION['username']);
      unset($_SESSION['userid']);

      /* Reflect fact that user has logged out */
      $this->logged_in = false;
      
      /**
       * Remove from active users table and add to
       * active guests tables.
       */
      $database->removeActiveUser($this->username);
      $database->addActiveGuest($_SERVER['REMOTE_ADDR'], $this->time);
      
      /* Set user level to guest */
      $this->username  = GUEST_NAME;
      $this->userlevel = GUEST_LEVEL;
   }

   /**
    * register - Gets called when the user has just submitted the
    * registration form. Determines if there were any errors with
    * the entry fields, if so, it records the errors and returns
    * 1. If no errors were found, it registers the new user and
    * returns 0. Returns 2 if registration failed.
    */
   function register($subuser, $subpass, $subemail){
      global $database, $form, $mailer;  //The database, form and mailer object
      
      /* Username error checking */
      $field = "user";  //Use field name for username
      if(!$subuser || strlen($subuser = trim($subuser)) == 0){
         $form->setError($field, "* Username not entered");
      }
      else{
         /* Spruce up username, check length */
         $subuser = stripslashes($subuser);
         if(strlen($subuser) < 5){
            $form->setError($field, "* Username below 5 characters");
         }
         else if(strlen($subuser) > 30){
            $form->setError($field, "* Username above 30 characters");
         }
         /* Check if username is not alphanumeric */
         else if(!eregi("^([0-9a-z])+$", $subuser)){
            $form->setError($field, "* Username not alphanumeric");
         }
         /* Check if username is reserved */
         else if(strcasecmp($subuser, GUEST_NAME) == 0){
            $form->setError($field, "* Username reserved word");
         }
         /* Check if username is already in use */
         else if($database->usernameTaken($subuser)){
            $form->setError($field, "* Username already in use");
         }
         /* Check if username is banned */
         else if($database->usernameBanned($subuser)){
            $form->setError($field, "* Username banned");
         }
      }

      /* Password error checking */
      $field = "pass";  //Use field name for password
      if(!$subpass){
         $form->setError($field, "* Password not entered");
      }
      else{
         /* Spruce up password and check length*/
         $subpass = stripslashes($subpass);
         if(strlen($subpass) < 4){
            $form->setError($field, "* Password too short");
         }
         /* Check if password is not alphanumeric */
         else if(!eregi("^([0-9a-z])+$", ($subpass = trim($subpass)))){
            $form->setError($field, "* Password not alphanumeric");
         }
         /**
          * Note: I trimmed the password only after I checked the length
          * because if you fill the password field up with spaces
          * it looks like a lot more characters than 4, so it looks
          * kind of stupid to report "password too short".
          */
      }
      
      /* Email error checking */
      $field = "email";  //Use field name for email
      if(!$subemail || strlen($subemail = trim($subemail)) == 0){
         $form->setError($field, "* Email not entered");
      }
      else{
         /* Check if valid email address */
         $regex = "^[_+a-z0-9-]+(\.[_+a-z0-9-]+)*"
                 ."@[a-z0-9-]+(\.[a-z0-9-]{1,})*"
                 ."\.([a-z]{2,}){1}$";
         if(!eregi($regex,$subemail)){
            $form->setError($field, "* Email invalid");
         }
         $subemail = stripslashes($subemail);
      }

      /* Errors exist, have user correct them */
      if($form->num_errors > 0){
         return 1;  //Errors with form
      }
      /* No errors, add the new account to the */
      else{
         if($database->addNewUser($subuser, md5($subpass), $subemail)){
            if(EMAIL_WELCOME){
               $mailer->sendWelcome($subuser,$subemail,$subpass);
            }
            return 0;  //New user added succesfully
         }else{
            return 2;  //Registration attempt failed
         }
      }
   }
   
   /**
    * editAccount - Attempts to edit the user's account information
    * including the password, which it first makes sure is correct
    * if entered, if so and the new password is in the right
    * format, the change is made. All other fields are changed
    * automatically.
    */
   function editAccount($subcurpass, $subnewpass, $subemail){
      global $database, $form;  //The database and form object
      /* New password entered */
      if($subnewpass){
         /* Current Password error checking */
         $field = "curpass";  //Use field name for current password
         if(!$subcurpass){
            $form->setError($field, "* Current Password not entered");
         }
         else{
            /* Check if password too short or is not alphanumeric */
            $subcurpass = stripslashes($subcurpass);
            if(strlen($subcurpass) < 4 ||
               !eregi("^([0-9a-z])+$", ($subcurpass = trim($subcurpass)))){
               $form->setError($field, "* Current Password incorrect");
            }
            /* Password entered is incorrect */
            if($database->confirmUserPass($this->username,md5($subcurpass)) != 0){
               $form->setError($field, "* Current Password incorrect");
            }
         }
         
         /* New Password error checking */
         $field = "newpass";  //Use field name for new password
         /* Spruce up password and check length*/
         $subpass = stripslashes($subnewpass);
         if(strlen($subnewpass) < 4){
            $form->setError($field, "* New Password too short");
         }
         /* Check if password is not alphanumeric */
         else if(!eregi("^([0-9a-z])+$", ($subnewpass = trim($subnewpass)))){
            $form->setError($field, "* New Password not alphanumeric");
         }
      }
      /* Change password attempted */
      else if($subcurpass){
         /* New Password error reporting */
         $field = "newpass";  //Use field name for new password
         $form->setError($field, "* New Password not entered");
      }
      
      /* Email error checking */
      $field = "email";  //Use field name for email
      if($subemail && strlen($subemail = trim($subemail)) > 0){
         /* Check if valid email address */
         $regex = "^[_+a-z0-9-]+(\.[_+a-z0-9-]+)*"
                 ."@[a-z0-9-]+(\.[a-z0-9-]{1,})*"
                 ."\.([a-z]{2,}){1}$";
         if(!eregi($regex,$subemail)){
            $form->setError($field, "* Email invalid");
         }
         $subemail = stripslashes($subemail);
      }
      
      /* Errors exist, have user correct them */
      if($form->num_errors > 0){
         return false;  //Errors with form
      }
      
      /* Update password since there were no errors */
      if($subcurpass && $subnewpass){
         $database->updateUserField($this->username,"password",md5($subnewpass));
      }
      
      /* Change Email */
      if($subemail){
         $database->updateUserField($this->username,"email",$subemail);
      }
      
      /* Success! */
      return true;
   }
   
   /**
    * isAdmin - Returns true if currently logged in user is
    * an administrator, false otherwise.
    */
   function isAdmin(){
      return ($this->userlevel == ADMIN_LEVEL ||
              $this->username  == ADMIN_NAME);
   }
   
   /**
    * generateRandID - Generates a string made up of randomized
    * letters (lower and upper case) and digits and returns
    * the md5 hash of it to be used as a userid.
    */
   function generateRandID(){
      return md5($this->generateRandStr(16));
   }
   
   /**
    * generateRandStr - Generates a string made up of randomized
    * letters (lower and upper case) and digits, the length
    * is a specified parameter.
    */
   function generateRandStr($length){
      $randstr = "";
      for($i=0; $i<$length; $i++){
         $randnum = mt_rand(0,61);
         if($randnum < 10){
            $randstr .= chr($randnum+48);
         }else if($randnum < 36){
            $randstr .= chr($randnum+55);
         }else{
            $randstr .= chr($randnum+61);
         }
      }
      return $randstr;
   }
};

/**
 * Initialize session object - This must be initialized before
 * the form object because the form uses session variables,
 * which cannot be accessed unless the session has started.
 */
$session = new Session;

class Form
{
   var $values = array();  //Holds submitted form field values
   var $errors = array();  //Holds submitted form error messages
   var $num_errors;   //The number of errors in submitted form

   /* Class constructor */
   function Form(){
      /**
       * Get form value and error arrays, used when there
       * is an error with a user-submitted form.
       */
      if(isset($_SESSION['value_array']) && isset($_SESSION['error_array'])){
         $this->values = $_SESSION['value_array'];
         $this->errors = $_SESSION['error_array'];
         $this->num_errors = count($this->errors);

         unset($_SESSION['value_array']);
         unset($_SESSION['error_array']);
      }
      else{
         $this->num_errors = 0;
      }
   }

   /**
    * setValue - Records the value typed into the given
    * form field by the user.
    */
   function setValue($field, $value){
      $this->values[$field] = $value;
   }

   /**
    * setError - Records new form error given the form
    * field name and the error message attached to it.
    */
   function setError($field, $errmsg){
      $this->errors[$field] = $errmsg;
      $this->num_errors = count($this->errors);
   }

   /**
    * value - Returns the value attached to the given
    * field, if none exists, the empty string is returned.
    */
   function value($field){
      if(array_key_exists($field,$this->values)){
         return htmlspecialchars(stripslashes($this->values[$field]));
      }else{
         return "";
      }
   }

   /**
    * error - Returns the error message attached to the
    * given field, if none exists, the empty string is returned.
    */
   function error($field){
      if(array_key_exists($field,$this->errors)){
         return "<font size=\"1\" color=\"#ff0000\">".$this->errors[$field]."</font>";
      }else{
         return "";
      }
   }

   /* getErrorArray - Returns the array of error messages */
   function getErrorArray(){
      return $this->errors;
   }
};

/* Initialize form object */
$form = new Form;

require_once ("functions.php");
require_once ("mailer.php");

?>