Question

I know, globals not (;

I am new to OOP, and I’m refactoring some functions I created into classes, but I come to a problem. Some of my classes are called from the pages themselves that the users enter (example: $Link->create('page/to/go');). Since this is outside any class, there’s no problem, the links get created.

But then, I have a class that attempts to login the user when created, and if the email entered is not in the database it redirects the user to the register page. Obviously, only doing header ('Location '.$Link->create('page/to/go')) does not work.

What I would do is to set the create method as static and then call it from everywhere. But I think this would be similar to using globals and I am trying to correct bad habits. So how should I do this?

Here’s some of the code for the class Link, implementing a 404-detect that I explained here:

class Link
  {
  private function valid($check)
    {
    $exceptions=array("help/report", "translate");  // More pages and rules to be added
    return in_array($check,$exceptions);
    }

  public function create($arg)
    {
      if (!file_exists("/path/to/".$arg) && !$this->valid($arg))
      {
      // Call a function to store the error in a database.
      error ("404 for ".$arg);

      // One way of handling it. Replace '/' for ' ' and google that string in this page.
      $arg=str_replace("/","%20",$arg);
      return "https://www.google.com/#q=site%3A".Configuration::get('BaseUrl')."%20".$arg;
      }
    else
      {
      // If the page exists or is an exception, create the normal link.
      if(empty($arg)) return Configuration::get('BaseUrl');
      else return Configuration::get('BaseUrl').$arg;
      }
    }
  }

As you can see in the code, when I implement error() into a class I will have a similar problem.

One option I just thought is that I might want to return an error and parse it from outside the __construct() of the User class. But it only works with this, as it’s a yes/not, and I don’t think making a error code up is proper for other cases.

So, what is your suggestion for passing properties and methods from one classes to others? Is it okay to use static for this context?

EDIT. The difficulty of my question it’s that, almost all book, tutorial, page etc I’ve seen talks about how to create a SINGLE class. I haven’t seen any explaining deeply how classes should talk to each other.

EDIT 2. As requested in the comments, here goes some more code. The user accesses his courses entering only the email (getting a level 1), while the user can only edit his settings if he gets a level 2 in the settings page. Not finished as I’ll put some more methods.

class User
  {
  private $Email;
  private $Name;

  public function __construct()
    {
    if (!empty($_POST['logout'])) session_destroy();
    else if ( !empty($_POST['email']) )
      {
      $this->loginEmail($_POST['email']);
      }
    else if ( $_SESSION['level'] == 1 )
      {
      if (!empty($_POST['password']))
        {
        $this->loginFull($_SESSION['email'],$_POST['password']);
        }
      else
        {
        $this->loginEmail($_SESSION['email']);
        }
      }
    else if ( $_SESSION['level'] == 2 )
      {
      $this->loginFull($_SESSION['email'],$_SESSION['pass']);
      }
    else session_destroy();

    }

  private function loginEmail($Email)
    {
    $sql=mysql_query("SELECT * FROM users WHERE email='".mysql_real_escape_string($Email)."'");  //Retrieve the entries from the database
    $row=mysql_fetch_assoc($sql);
    if(mysql_num_rows($sql)==1)
      {
      $this->getData($row);
      $_SESSION['level']=1;
      }
    else header ('Location: http://example.org/new/student/');
    }

  private function loginFull($Email,$Pass)
    {
    $sql=mysql_query("SELECT * FROM users WHERE email='".mysql_real_escape_string($Email)."' AND pass='".md5($Pass)."'");  //Retrieve the entries from the database
    $row=mysql_fetch_assoc($sql);
    if(mysql_num_rows($sql)==1)
      {
      $this->getData($row);
      $_SESSION['pass']=$Pass;
      $_SESSION['level']=2;
      }
    else $this->loginEmail($Email);
    }

  private function getData($row)
    {
    $_SESSION['email']=$row['email'];
    $this->Email=$row['email'];
    $this->Name=$row['name'];
    }

  public function get($Var)
    {
    return $this->$Var;
    }
  }

And now the class Error. As you can see, I already performed some DI without even knowing about it here.

class Error
  {
  private $Page;
  private $Language;
  private $User;

  public function __construct($Page,$Language,$User="None")
    {
    $this->Page=$Page;
    $this->Language=$Language;
    $this->User=$User;

    if (!empty($_REQUEST['banner']))
      $this->Banner=$_REQUEST['banner'];
    }

  public function add($Kind)
    {
    if (!mysql_query("INSERT INTO error (kind, page, lang, user, version, date) VALUES ('".mysql_real_escape_string($Kind)."', '".mysql_real_escape_string($this->Page)."', '".mysql_real_escape_string($this->Language)."', '".mysql_real_escape_string($this->User)."', '".Configuration::get('Version')."',NOW() )"))

    mail(Configuration::get('ErrorEmail'), "Error '".$Kind."' that couldn't be stored.",
       "Full url: ".$FullUrl."\n Language: ".$this->Language->Lang."\n User: ".$Identif."\n Version: ".$Version);  // Inform of the error by email
    }
  }

Answer 1

Create instance of Link class and pass it to where it is needed (using setter or constructor).
Definitelly read something abou DI (Dependency Injection) and then DI Containers.

Nice introduction in Nette Framework – Dependency Injection