Not accessing class attributes and methods as I expected for Logging system

sfc · July 2, 2010

I am very much in the learning process of PHP and programming in general. I have a feeling if I get this concept I will be well on my way so your help is greatly appreciated.

I want to write a line to my "log.txt" file whenever someone logs in. Can you help me figure out what I am doing wrong? This is all experimental and is not heading for production, at least not for a long time.

Here is the error I am getting:

Notice: Undefined variable: user_id in C:\wamp\www\photo_gallery\includes\session.php on line 25

Fatal error: Cannot access empty property in C:\wamp\www\photo_gallery\includes\session.php on line 25

Here is the login.php file:

<?php
require_once("../../includes/initialize.php");   

if($session->is_logged_in()) {
redirect_to("index.php");
}

//Check to see if page was submitted
if(isset($_POST['submit'])) {

$username = trim($_POST['username']);
$password = trim($_POST['password']);

//Check database to see if username/password exist.

  $found_user = User::authenticate($username, $password);
  
  if($found_user) {
  $session->login($found_user);
  //header("Location: index.php");
  }  else {
  $message = "Username/password combination incorrect.";
  }


} else {

$username = "";
$password = "";
}
?> 
<html>
<head>
<link href="../stylesheets/main.css" media="all" rel="stylesheet" type="text/css" />
<title>Photo Gallery</title>
</head>
<body>
<div id="header">
<h1>Photo Gallery</h1>
</div>
<div id="main">
<h2>Staff Login</h2>
<?php echo output_message($message)?>

<form action="login.php" method="post">
<table>
	<tr>
		<td>Username:</td>
		<td>
			<input type="text" name="username" maxlength="30" value="<?php echo htmlentities($username); ?>" />
		</td>
	</tr>
	<tr>
		<td>Password:</td>
		<td>
			<input type="password" name="password" maxlength="30" value="<?php htmlentities($password); ?>" />
		</td>
	</tr>
	<tr>
	<td colspan="2">
		<input type="submit" name="submit" value="Login" />
	</td>
	</tr>
</table>
</form>
</div>
<div id="footer">
Copyright <?php echo date("Y", time()); ?>
</div>
</body>
</html>

<?php if(isset($database)) { $database->close_connection();} ?>

Here is the initialize.php:

<?php

defined('SITE_ROOT') ? null : define('SITE_ROOT', "/" . 'wamp' . "/". 'www' . "/" . 'photo_gallery' );

defined('LIB_PATH') ? null : define ('LIB_PATH', SITE_ROOT . "/" . 'includes');

require_once(LIB_PATH."/"."config.php"); 
require_once(LIB_PATH."/"."functions.php");  
require_once(LIB_PATH."/"."session.php"); 
require_once(LIB_PATH."/"."database.php");
require_once(LIB_PATH."/"."database_object.php");
require_once(LIB_PATH."/"."user.php");
require_once(LIB_PATH."/"."logger.php");
?>

Here is the user.php:

<?php
// If it's going to need the database, then it's 
// probably smart to require it before we start.
require_once(LIB_PATH."/".'database.php');

class User extends DatabaseObject {

	public $id;
	public $username;
	public $password;
	public $first_name;
	public $last_name;



	public function full_name() {
		if(isset($this->first_name) && isset($this->last_name)) {
			return $this->first_name . " " . $this->last_name;
		} else {
			return "";
		}
	}

	public static function authenticate($username="", $password="") {
		global $database;
		$username = $database->escape_value($username);
		$password = $database->escape_value($password);

		$sql  = "SELECT * FROM users ";
		$sql .= "WHERE username = '{$username}' ";
		$sql .= "AND password = '{$password}' ";
		$sql .= "LIMIT 1";
		$result_array = self::find_by_sql($sql);
		return !empty($result_array) ? array_shift($result_array) : false;
	}


}

?>

Here is the session.php:

<?php
require_once("logger.php");
// A class to help work with Sessions
// In our case, primarily to manage logging users in and out

// Keep in mind when working with sessions that it is generally 
// inadvisable to store DB-related objects in sessions

class Session {

private $logged_in=false;
public $user_id;

function __construct() {
	session_start();
	$this->check_login();
if($this->logged_in) {
  // actions to take right away if user is logged in
} else {
  // actions to take right away if user is not logged in
}
}

public function return_userid() {
	  return $this->$user_id;
}
  public function is_logged_in() {
return $this->logged_in;
  }

public function login($user) {
// database should find user based on username/password
if($user){
  $this->user_id = $_SESSION['user_id'] = $user->id;
  $this->logged_in = true;
  logger::log_action("logged in");
}
  }
  
  public function logout() {
unset($_SESSION['user_id']);
unset($this->user_id);
$this->logged_in = false;
  }

private function check_login() {
if(isset($_SESSION['user_id'])) {
  $this->user_id = $_SESSION['user_id'];
  $this->logged_in = true;
} else {
  unset($this->user_id);
  $this->logged_in = false;
}
  }
  
}

$session = new Session();

?>

Here is the logger.php:

<?php (LIB_PATH."/".'session.php'); 
  
  class logger {
  
  private static $file =  "/wamp/www/photo_gallery/logs/log.txt";
  
  static function log_action($action="", $message = "") {
			global $session;
		  $handle = fopen(logger::$file, 'at');
		  fwrite($handle, date("Y-m-d H:i:s"). "| Login: " . $session->return_userid() . " " . $action. "\n");
		  fclose($handle);	
	  }
	  
  }
  
  
?>

Adam · July 2, 2010

Should be:

return $this->user_id;

sfc · July 2, 2010

Thanks...sorry for the stupid miss.

I do have another question: Why is this not working in my logger.php file?

 private static $file = SITE_ROOT . "/logs/log.txt";

In the initialize.php file I define SITE_ROOT as:

defined('SITE_ROOT') ? null : define("SITE_ROOT", "/" . 'wamp' . "/". 'www' . "/" . 'photo_gallery' );

Thanks

Adam · July 2, 2010

Define 'not working'..

sfc · July 2, 2010

Parse error: syntax error, unexpected '.', expecting ',' or ';' in C:\wamp\www\photo_gallery\includes\logger.php on line 6

sfc · July 2, 2010

i figured out that I needed to define a variable outside of the class

Like this:

<?php 
require_once(LIB_PATH."/".'initialize.php'); 

$file =  SITE_ROOT . "/logs/log.txt"; 
  
  class logger {
  
  
  
  static function log_action($action="", $message = "") {
			global $session;
			global $file;

		  $handle = fopen($file, 'at');
		  fwrite($handle, date("Y-m-d H:i:s"). "| ". $action . " " . $message. "\n");
		  fclose($handle);	
	  }
	  
  }
  
  
?>

But I don't understand why if I have defined a constant I can't use it in a class. Is there a way to do this because I would prefer to keep $file private.

Thanks.

Cagecrawler · July 2, 2010

When declaring a class property, the value must be constant, ie. it can't depend on run-time information. From the PHP manual:

<?php
class SimpleClass
{
   // invalid property declarations:
   public $var1 = 'hello ' . 'world';
   public $var2 = <<<EOD
hello world
EOD;
   public $var3 = 1+2;
   public $var4 = self::myStaticMethod();
   public $var5 = $myVar;

   // valid property declarations:
   public $var6 = myConstant;
   public $var7 = array(true, false);

   // This is allowed only in PHP 5.3.0 and later.
   public $var8 = <<<'EOD'
hello world
EOD;
}
?>

sfc · July 2, 2010

So I just did this:

$file =  SITE_ROOT . "/logs/log.txt";

like this:

<?php 
require_once(LIB_PATH."/".'initialize.php'); 


  
  class logger {
  
  
  
  static function log_action($action="", $message = "") {
			global $session;

			$file =  SITE_ROOT . "/logs/log.txt"; 

		  $handle = fopen($file, 'at');
		  fwrite($handle, date("Y-m-d H:i:s"). "| ". $action . " " . $message. "\n");
		  fclose($handle);	
	  }
	  
  }
  
  
?>

I'm not clear on why this works. Why does

$file = ...

work but

private static $file = SITE_ROOT . "/logs/log.txt";

doesn't? I understand what Cagecrawler posted...but what is the difference between the two variables. Clearly they are being defined differently but I'm not totally understanding how PHP views the two definitions.

Thanks for your help.

Cagecrawler · July 2, 2010

In your example, $file is simply a variable within the function. It only exists within the scope of the function (ie. you couldn't use $this->file). When you define it outside of the function but inside the class (as private static) PHP doesn't see it as a normal variable but as a property of the class. You can now use it anywhere in the class (as $this->file) and any value you give it will persist as long as the instance of the class remains.

sfc · July 2, 2010

Yes...I didn't notice that I dropped it into the function...that makes sense.

Thanks...I'm starting to get my mind wrapped around this stuff.

sfc · July 2, 2010

So I thought I was cool but what do I do if I want the variable to be a class attribute that is usable by the rest of the functions in the class so I only have to load the path once?

I tried this:

<?php 
require_once(LIB_PATH."/".'initialize.php'); 



class logger {

private static $file;

	 function __construct() {
		static::$file =  SITE_ROOT . "/logs/log.txt";
	}

	static function log_action($action="", $message = "") {
		global $session;



		$handle = fopen( static::$file, 'at');
		fwrite($handle, date("Y-m-d H:i:s"). "| ". $action . " " . $message. "\n");
		fclose($handle);	
	} // End of log_action() function

	static function log_exists() {

		if (!static::$file) {

		}

	} // End of log_exists() function

	static function read_log() {

	}  // End of read_log() function



} // end of logger class


?>

But it didn't work, meaning that it didn't write to the file.

Cagecrawler · July 3, 2010

Remove the static keyword on $file, and then refer to it as $this->file rather than static::$file (which should actually be self::$file anyway). Only use static properties if you want to access them independantly of the class which the private property would block anyway.

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Not accessing class attributes and methods as I expected for Logging system

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