A wrapper class for Sessions in PHP

Question

I have been using $_SESSION, $_POST, $_GET, $_SERVER globals directly without ever knowing there was a concept/practice called, "Wrapping globals in classes" until, yesterday. As I did, I was able to immediately understand its effective benefit / usefulness. But I searched for a good wrapper, for $_SESSION, $_GET and $_POST but could not find anything simple/good. So, as a test I made this for the session global.

<?php 
/**
 * A SESSION Wrapper class. 
 * 
 * @category Session
 * @version 1.0.0
 * @Nile
 */
namespace Nile\Lib; 
class Session
{
 protected static $sessionLife = 1200; 
 public static function start()
 {
 if(!headers_sent() && !session_id()){
 if(session_start()){
 session_regenerate_id();
 return true; 
 }
 }
 return false; 
 }
 public static function set($Key, $value)
 {
 $_SESSION[$Key] = $value; 
 }
 public static function has($Key)
 {
 return (bool)(isset($_SESSION[$Key])) ? $_SESSION[$Key] : false; 
 }
 public static function get($Key)
 {
 return (isset($_SESSION[$Key])) ? $_SESSION[$Key] : false; 
 }
 public static function del($Key)
 {
 if(isset($_SESSION[$Key])){
 unset($_SESSION[$Key]);
 return false; 
 }
 }
 public static function destroy()
 {
 if(isset($_SESSION)){
 session_destroy();
 } 
 }
 public static function dump()
 {
 if(isset($_SESSION))
 {
 print_r($_SESSION); 
 return ;
 }
 throw new \Exception("Session is not initialized");
 }
}

And this is the simple session initialization.

Session::start(); // does session_start(); 
Session::set('user', 'isLogedIn'); //does $_SESSION['user'] = 'isLoggedIn'; 

Considering this is my first wrapper, I would like a review and what I could add next. Something that is not very complicated, just easy to understand and a useful feature for this class.

• cHao: The question that really needs answering is: How does Session justify its existence? How is code that uses it simpler and/or more useful than code that uses $_SESSION? What have you abstracted away?
• alexw: How about having your class implement ArrayAccess?

Answer 1

I have been using php for over 10 years and never found a need for a session wrapper, but maybe you find it easier/better.

There are a few improvements that could be made with your code

If we are checking to see if the session has a key, a simpler test is

public static function has($Key)
{
 // return (bool)(isset($_SESSION[$Key])) ? $_SESSION[$Key] : false; 
 return array_key_exists($Key, $_SESSION); 
}

The get function here would probably be more useful with a default value option then just returning false.

public static function get($Key, $default=false)
{
 return (self::has($Key)) ? $_SESSION[$Key] : $default; 
}

The del function, I am unsure what you are trying to achieve by returning false, but returning nothing if it isn't set? Personally I wouldn't bother to check if it is set or not, just unset it, and return nothing. I would also call it delete, so it is painfully obvious to the use what it does

 public static function delete($Key)
 {
 if(isset($_SESSION){
 unset($_SESSION[$Key]);
 // return false; 
 }
 }

The dump function, why do you throw an exception if the session doesn't exist, but not anywhere else if the session doesn't exist? I would re-write it like a guard clause rather then having a return halfway through the function.

public static function dump()
{
 if(!isset($_SESSION))
 {
 throw new \Exception("Session is not initialized");
 }
 print_r($_SESSION);
}

Another useful function you might add is get_once. I do something similar for when I store an error message in the session, then redirect to a new page and display the error message. After that the error message is no longer relevant so I remove it from the session.

public static function get_once($Key, $default=false)
{
 $value = self::get($Key, $default);
 self::delete($Key);
 return $value;
}

Other things you could do is to manage different "namespaces" (maybe not the best word to describe it) within a session.

// keep in mind if you do this, you can't use static everywhere like you have
function __construct($namespace) {
 $this->namespace = $namespace;
}
function set($key, $value) {
 $_SESSION[$this->namespace][$this->key] = $value;
}
// Then you can use simple keys that don't overwrite each other
$user_session = new session('user');
$user_session->set('name', 'Donald Duck');
$page_session = new session('page');
$page_session->set('name', 'Home Page');

• robue-a7119895: Thanks. I made a quick mistake with the exception and your third example. Good catch about the message management, although I am sure it does contradict SRP. Anyway, if you have more let me know.
• Vladimir Vukanac: Returning default false can be confusing as false is proper value with some meaning. Think to use null as default.
• bumperbox: @mrW good point, but unfortunately null is also a proper value as such, so you can't win some times.
• bumperbox: If i had used array_key_exists() instead of isset() in the has() function, then at least the check could be made, even if the value stored is null
• Vladimir Vukanac: @bumperbox, I agree.